Costco Wholesale (COST) reported that its net sales rose an annualized 7.1% to $19.80 billion U.S. in August as consumers continue to flock to the warehouse club for groceries and other essential items. The August sales result follows a 7% year-over-year increase recorded by the company in July of this year. Costco is one of the few publicly traded companies that continues to report its financial results on a monthly as well as quarterly basis. Despite the strong overall results for August, Costco’s same-store sales dipped slightly due to lower gas prices. A decline in gas prices averaging 11…