From your comment I assume you are American, since I heard that people pack your bags at your stores. In Germany and probably most of Europe a typical checkout process works differently and probably solves the problem.

1. You put your stuff on a large transport band, emptying your cart (probably have those as well)
2. When you're up you move your cart at the large area after the cashier
3. The cashier registers everything and pushes it to you into that big area
4. You put everything in your bags while they are working
5. Cashier finishes, you make your payment
6. You pack the last 3 items that are remaining

Some stores also introduced a simple "switch" that makes the products of the person after you slide into a seperate area, to save time .