Carson City saw a 3.6 percent increase in taxable sales in December, reporting a total of $72.6 million in sales.The biggest driver in that increase was the 21.4 percent jump in auto sales, which came in just over $18 million. The only other major category in the capital to see a solid increase was food services and drinking places — up 4.2 percent to $7.4 million.The other major category, General Merchandise Stores, increased just 0.4 percent to $16.89 million. Wholesalers of both durable and nondurable goods were down.Statewide, merchants sold $4.3 billion in goods in December, on which the state …