That's happened to me and I told the cashier to add stuff to my purchase after I've paid it. She said that she had to re-scan everything and re-enter the coupons...and it took over 30 minutes...but I got my 20x the points in the end. Normally we'd be happy when something is cheaper than written on the shelf...but not when we've got everything calculated to the dot and it's cheaper lol. Next time