After two separate requests this week for assistance on grocery-related projects, I thought I'd post an older example from last summer's beta.
The idea is you drag items over a scanner to read their price. If you drop the item in the grocery bag, the price is added to the total. If you don't drop the item in the bag, the price isn't added to the total.
Finally, after all items are placed in the bag, a checkout button appears and you can load your car. Wish I had a car with both an open closed trunk. No, I'm not lazy to go take pics of my own car... It's just that I'd have to clean it out, first.
Oh, and one more thing: don't even think about stealing any of the groceries.