The Supreme Court declined yesterday to distrub the conviction of an Internal Revenue Service official in Pittsburgh who admitted receiving hundreds of gifts worth $7,445 from Gulf Oil Corp. during an eight-year period when he headed a team of IRS agents responsible for auditing its tax returns.

Large-case manager Cyril J. Niederberger was convicted of six counts of accepting illegal gratuities - specifically, five golfing junkets to plush resorts - for and because of official acts that he performed. Each junket coincided with the opening or closing of a particular audit of the company.

He drew six months in prison, a $5,000 fine, and five years on probation. His salary in 1975, when the eight-year period ended, was $31,552. The conviction was upheld last May by the 3d U.S. Circuit Court of Appeals. Now 70, he retired before he was convicted.

The first junket, in January 1973, was a four-day outing at the Doral Beach Country Club in Miami Beach. The bill was charged to the American Express card of his companion, John F. Fitzgerald, Gulf's manager for federal tax compliance.

Several months later, Niederberger and his wife spent four days at the Seaview Country Club in Absecon, N.J., with Fred W. Standefer, Gulf's vice president for tax administration. The bill went for payment to Arthur V. Harris, Gulf's manager of government relations.

Niederberger admitted he knew that his acceptance of gratuities was a criminal act, but argued for overturn of his conviction on the partial ground that the government hadn't proved he'd performed "some specific official act" as the "quid pro quo" for the gifts.

Solicitor General Wade H. McCree Jr. said that the government had proved all that the law required. In a petition to let the conviction stand, he told the Supreme Court that Niederberger obviously "was not being lavishly and expensively entertained to foster general good will. The gratuities related directly to his official action in connection with the Gulf tax adudits." Federal Reserve

The court let stand a ruling that Rep. Henry Reuss (D-Wis.) does not have the right to challenge the constitutionally of the method used to select five members of the Federal Reserve System's Open Market Committee - those elected annually by the boards of some 6,000 Federal Reserve member banks.

Reuss, chairman of the House Banking, Currency and Housing Committee, argued that the five are "officers of the United States" and, consequently, subject to nomination by the President. Rail Strikes

The court declined to distrub rulings that the federal courts are not empowered to prevent railroad unions from striking and picketing their employers to protest an industry-wide strike insurance program. John's Bargain Stores

The court let stand the conviction of Gerald Sprayregen for fraud involving the now-bankrupt John's Bargain Stores Corp., a unit of the Straton Group, Ltd., that operated more than 200 discount outlets.

He was sentenced to serve one-year concurrent sentences on each of 11 counts. The 2d U.S. Circuit Court of Appeals in New York City upheld the conviction last May.

Sprayregen, although chairman of Stratton, swore to the jury that he neither knew of nor participated in falsifying its financial statements for 1972 and the first quarter of 1973.

The statements, filed with the Securities and Exchange Commission, First Pennsylvania Bank & Trust Co., and credit agencies, enabled Sprayregen to receive a large loan.

At the trial, Sprayregen's testimony was contradicted by two of John's officials, comptroller Jose Umana and post-1972 operations vice president Walter Spengler, who pleaded guilty to fraud and became government witnesses.

They told that jury that immediately after acquiring control of John's in 1969, a group of investors allied with Sprayregen joined with John's president David Cohen in making a commitment to buy Sprayregen's brokerage firm for $15 million.

Concerned by the commitment, suppliers started to deny credit to John's throughout 1970, as a result, store managers were forced to buy inferior merchandise that then stagnated on the shelves.

To revitalize the chain, Sprayregen and Spengler cut prices to generate volume and cash, but the result was a $1.8 million loss.

The case against Sprayregen involved efforts to conceal the loss by manipulating the amount of money credited to inventory. Bargain Oil Leases

In 1969, Champion Oil Co. of Alaska accepted a state invitation to bid on oil and gas leases by offering $1 for each of 179 tracts. Champion turned out to be the sole bidder on the tracts.

The state rejected the bids on the ground that the law empowered it to turn away apparent high bids "not in the best interest" of Alaska.

After nine years of litigation, the state's highest tribunal ruled against Champion. The Supreme Court let the decision stand.