Last-minute Christmas shoppers, attracted by large discounts and round-the-clock promotions, made the holidays surprisingly cheerful for most local retailers.

Merchants who had nervously watched the pace of Christmas sales in the wake of October's stock market plunge reported yesterday that shoppers came through after all -- even though the sales came later than the retailers had hoped.

"The last four days were very strong, and that's what made the season," said Richard Hindin, president of Britches of Georgetowne. "We were inching right along, and then we closed with a bang." Hindin said he expects the chain's December sales to be up 12.6 percent over last year.

Although that increase is well below the 16 percent sales gain that Britches has posted for all of 1987 to date, "that was about the plan" for December, Hindin said.

Like most other retailers, Britches had been anticipating more sluggish sales in December because of an expected slowdown in consumer spending.

To guard against the effects of sluggish sales, retailers ran more promotions and cut prices sharply.

At The Hecht Co., sales promotions and the opening of two new stores gave the chain sales increases "well into the double digits" over last year's figures, according to Chairman J. Warren Harris.

"We had a fantastic Christmas, much greater than expected," Harris said.

For the first time in more than a decade, retailers had expressed strong doubts about the holiday season only days before it began in earnest in November. The retailing business already was showing signs of weakness before the stock market drop in October, and retailers feared that Black Monday would only worsen what already looked like a dreary Christmas.

But retailers yesterday were relieved. Although some reported only moderate sales increases -- just barely keeping up with their plans and inflation -- others reported unexpectedly strong double-digit gains.

"We couldn't be more pleased," said Michael Sullivan, president of Merry-Go-Round Enterprises Inc. of Towson. "Last year, we had our best Christmas ever. This year we did even better, with a 20 percent increase overall and low double-digit gains for stores open more than a year." The last is a critical measurement for retailers.

"We woke up Saturday morning and thanked the Lord that we had no major bad weather," Sullivan added. "If we had gotten Monday's weather last week, we would have been in trouble."

"The last 10 days before Christmas were absolutely what the doctor ordered," said Harold Nelson, vice president and general manager of Neiman-Marcus at Mazza Gallerie in Washington.

"There was still caution and fastidiousness in customers picking out the proper gift, but sales were above our expectations and well within our profit plan," said Nelson, who declined to give precise figures.

Other retailers were more restrained. "We made our plan, which was modest," was all that a local J.C. Penney Co. official would say about sales this month.

Similarly, Bradlees and Sears, Roebuck & Co. noted that their gains were moderate this month.

Meanwhile, at Woodward & Lothrop Inc. sales last week "were strong and post-Christmas sales on Saturday and Sunday were very strong," said Robert Kiatta, Woodies' senior vice president for stores. "We will make our plan for the month. However, it was not an aggressive plan." Like other retailers, Woodies added more items to its planned sales promotions to attract shoppers.

About a third of retail sales come in November and December. Because consumer spending accounts for about two-thirds of the economy, economists were watching holiday sales to determine the direction of the economy next year. Sales declines could signal a recession.

"Overall, sales volume {nationally} doesn't appear to be much different than a year ago, with sales up not much more than inflation, which is running at 4 percent," said David Wyss, chief financial economist of Data Resources Inc., a Lexington, Mass., consulting firm.

Even so, Wyss said, sales data shows, "The economy is pointing to a slowdown, but not to a recession."

According to Michael Lavington, president of Kay Jewelers Inc., consumers spent more in the Washington area than other parts of the nation. "In this area, sales were up 19 percent in December, a bit better than the whole country, where sales increased 15 percent," he said.

By either standard, however, sales were far better than the 9 percent increase for which Kay had planned. Lavington attributed the steep increase in part to a sharp rise in sales of more expensive jewelry.

Similarly, the local Melart Jewelers Inc. chain reported sales increases twice as strong as expected, with sales up 10 percent. However, unlike at Kay, Melart Chairman Albert A. Foer said transactions were smaller than anticipated.