May 2nd through 15th, buy a $25 Roots or Old Navy/Gap/Banana Republic gift card for just $20.  This offer is not valid on any other denomination of gift card but you can buy more than one.

These stores always have sales and discount coupons, so stock up on some gift cards now and combine the 20% discount on the card with their next special offer to save even more.

My Sobeys tend to sell out of sale gift cards quickly.  If you are not shopping at the start of the promotion, you may want to call your local store and check with customer service to make sure they still have some, especially if you want to buy extras.