I went to the Walmart this morning but for a while I thought I might be in a casino in Las Vegas.
I used one of the automated checkouts and decided to use cash rather than my Visa card. The total came to something like $6.53. I put 3 cents in first but the machine responded by pumping out something like 53 cents. I kept at it, putting in a $5 and a $1 and then adding coins to try to meet the required total. The machine would reject some of the coins and give me more back. It was rather like playing a slot machine and if you won you got to keep your groceries. Finally I managed to satisfy it, by which time I had no idea how much I had paid but I was pretty sure that it was less than it should have been. I told one of the Walmart people that the thing was acting weird but that I was entirely satisfied with the results.
So you suppose that all such machines are hooked together and if they recognize you they give back the money they shorted you on in previous encounters?