"ON THE WHOLE, 1985 has been kind to small business. Sales and profits grew. Costs rose only moderately. Interest rates were manageable. Small-business specialist William C. Dunkelberg, economist for the National Federation of Independent Business, the nation's largest small-business association, says, ""Overall I think it was a very good year.""</br></br>But many small-business owners are uneasy about 1986. A year ago, NFIB's quarterly survey of 8,000 of its more than 500,000 members found 58% expecting business conditions to improve in the next 12 months. That dropped to 19% in the latest poll. Mr. Dunkelberg, a professor at Purdue University, says, ""There has been a substantial loss in confidence.""</br></br>One reason is the economy's four-year string of strong performance. ""A lot of people don't think it can continue,"" he says. Also, owners are worried about the growing federal deficit, the nation's continuing foreign-trade deficits, problems in the banking industry and the prolonged slump in agriculture. ""Next year,"" the economist says, ""doesn't look that exciting.""</br></br>---</br></br>TALLGRASS TECHNOLOGIES CORP. will remember 1985 as the year the bubble burst. The Lenexa, Kan., computer-accessory company was experiencing incredible growth when it was mentioned here a year ago. Sales had taken off from $1 million in 1982 and were expected to total $60 million for the year ended last June 30."