Gas prices are rarely a place to find good news, particularly with credit card surcharges and steadily rising prices. But regardless of whether the price is low or high, you’ve probably noticed that gas stations always tack on a peculiar charge to their listed cost. The Revenue Tax Act of 1932 allowed for a federal tax of $0.01 to be placed on gas prices to help offset the national debt. Gas stations can’t round down because their profit margins on gas are slim enough as it is. By one estimate, gas stations make only five cents per gallon in profit, so lopping off a cent is like giving away 20 percent of sales.