Pennies cost more to make than what they are worth as a unit of currency. They are a burden to many. If the penny was deemed obsolete, then all pennies should be gathered up and melted, to the zinc and copper elements, and used elsewhere.
Stores could easily round up or down to the nearest 5c, in order to keep prices high for profit. Remember the half-penny? That was able to buy more than what the current penny can buy when it was cancelled.