In Quebec, Canada, if an item in the store has a shelf price that is higher then the one that is scanned at the register, the store has to give it to you for free if it is under 10$ or has to give a rebate of 10$ on the lowest price.

If the scanned price is lower then the price indicated, the customer gets the lowest price.

Most big surface store (Loblaws, Super C, et al) have often problems with the pricing and I won't refuse any rebate that comes my way because of their incompetence.

For me, the same applies to any purchase I make. If the company can't get it's pricing act together, then I shouldn't be the one paying for it.