Business inventories in September rose 0.7 per cent while sales were virtually unchanged, the government said yesterday.

While the $21 billion inventory growth to nearly $328 billion was slightly below August's 0.8 per cent, it was still a relatively healthy gain, economists said. Total sales reached $223,5 billion in September, nearly matching August's record $223.6 billion, the Commerce Department said.

Retail sales were unchanged in September, but figures released last week for October showed a gain of 1.8 per cent.

Manufacturer's sales increased 0.2 per cent, while wholesaler's declined 0.5 per cent, the department said.

The total business stock-to-sales ratio at the end of the month was 1.47 compared with 1.46 in August and 1.51 in September 1976. The ratio indicates that for every $100 for goods sold, businesses had $147 in goods on hand.

Retail inventories of durable goods fell by $57 million in September compared with a rise of $447 million in August. Nondurable inventories gained $615 million in September compared with an $877 million increase in August.

The department said wholesale inventories of durable goods increased $67 million in September compared with a $922 climb in the preceding month. Wholesale nondurables gained $221 million, following a $107 million decrease in August.

Manufacturers' inventories of durable goods rose $380 million compared with a $474 million gain in August.

The report said retail sales of durables fell 1.2 per cent in September after a 2.5 per cent increase in August. Nondurables climbed 0.5 per cent following a static report of August.