> listed on the shelf at $5, rang up at $7.65. Bounty paper towels, shelf price $10.99, rang up at $15.50

I'm sure the US obsession with not putting the actual price (tax included) on the shelf helps a lot with this. I would notice quite quickly if a store would systematically overcharge me in Europe. It'd be much harder in the US where I expect the price on the shelf to not match the price at checkout.