The supermarkets in the US have this Self checkout option, to avoid making their customers wait in the forever serpentine queues. All items, except discrete vegetable and fruits have a bar code on them and you would scan the bar code.
The experience last week at the 'Always Low prices' store was not all that desirable. We keyed in the bar code number more number of times, than actually scanning the barcode. The machine/bar-code reader isn't sensitive at all, and even a Walmart employee who came to help, couldn't do it himself. It was worse, if one got multiple quantities of the same thing, since it didn't scan the second or the third piece of the same item. I wonder how cashiers do it all the time. Hats off to their efficiency.
At the Food and drug store, it is way better off, though I've faced the same problem, but not to this magnitude.