Wal-Mart Stores, the worldÔÇÖs largest retailer, and Costco Wholesale said September sales rose as cash-strapped consumers worried by the Wall Street crisis looked for discounts on food and toiletries. ┬á Wal-MartÔÇÖs sales rose 2.4 percent for the month at stores open at least a year while Costco reported a 7 percent monthly sales increase.