LELAND -- If you shop at Wal-Mart at the Leland store location check your receipts to make sure you were charged the correct sales tax. The store became aware of the problem after a customer says Wal-Mart charged him a sales tax of 7.75 percent instead of 6.75. A store spokesperson says the mistake has been fixed in the registers. The store encourages you to bring in receipts for a refund.