Country is out, jazz is in, but rock still rules at the cash register, according to a recently released survey of 1986 record sales by the National Assn. of Recording Merchandisers. Pop-rock music accounted for 53% of all sales. Black music was a distant second with 10% of sales. Country music, which accounted for 9% of retail sales two years ago, fell to 5%. Jazz jumped from 3.7% to 8%. Sales of compact discs soared 700%, accounting for 27% of sales; in 1984, CD sales amounted to a paltry 4%.