WESTMINSTER

Taxable retail sales in the city were up 11.6% in the third quarter of last year, compared with the same quarter in 1997, according to a financial report released by the city. The report, by the HDL Cos., said the largest increases included the categories of office supplies and furniture--up 211%--and discount department stores--up 76.2%. The largest business group, new auto dealers, was up 10%, partly due to an increase in dealers. Throughout the state, taxable retail sales increased an average of 5.26%.