In one situation, one of the items I purchased did not trigger the reward amount. I noticed the problem and the cashier helped me resolve it so I received the reward amount and the correct price on the item. In another situation, one of the items on a Buy 4 and Save deal did not trigger the $2 savings. Not only did I did not received the $2 off, but the item also rang up nearly $3 over the correct price. I noticed this issue and talked to customer service. They were able to a provide for a refund for the difference in price and the amount of the deal. Some stores will even offer full refund when the price is incorrect in their system.
I saved over $8 dollars this week (10% of my grocery trip) simply by looking at the receipt and making sure my items rang up correctly. On top of that my husband saved another $1 when his watermelon rang up incorrectly and he brought it to the cashier's attention.
This tip does not require any coupons and anyone can do it, but it does require that you look closely at your receipt before you leave the store or once you reach your car.