Many times, I am in an express lane with one item in behind people with full shopping carts. I have always felt that the people with more items than the number of items per lane should be charged a 10% convenience fee per items. (If somebody had 20 items in a 10 item or less lane would pay a 100% fee (doubling their pre-fee total, 30 items would triple their cost, etc). Any fees gathered will go to the federal tax base.
This will assist in teaching at least one basic math skill (counting), help speed up commerce (people with too may items will go to the correct lane), and increase the federal tax base without unduly taxing the undeserving.