The following applies in the province of Quebec (Canada).
In principle, the Consumer Protection Act (CPA) requires merchants to label the price on each article, but allows for exceptions. For example, because of the increasingly popular use of optical scanners, retailers are no longer required to label each article; several avail themselves of this exemption, but are still subjected to a number of constraints that include, amongst others, mandatory display of each article’s price on the shelf and of a sign about the Price Accuracy Policy.
This policy includes measures to compensate the consumer in the event of any inconsistency between the price on the shelf, and that charged by the register.
If the product price is $10 or less, the merchant must give you the item for free.
If the product price is more than $10, the retailer must sell you product at the price displayed on the shelf and further give you a $10 discount.