I was on line at Walmart at the self checkout when an elderly man came up behind me with a couple of items in his hands. I insisted the he go before me since I had a cart full of groceries. He checked his items but tried to use a ten dollar bill to pay. There was a sign above the machine stating machine only takes cards. After canceling the process, he re-scanned his items and tried to pay with a card. The card was rejected twice. I said I would use my card and pay for his items as an