Via Laptop Travel, Office Depot / Max are offering a promotion for $10 of $50 in Mastercard gift cards.
The way the register works, you can purchase a single $100 (or $200) Mastercard gift card and receive two “$10 off $50” discounts for a total of $20 off. The limit is supposed to be two discounts per household, but you may have luck with the cashier letting you purchase more. If so, they will need to be rung up one at a time for you to receive multiple $20 discounts. The deal is valid through 4/15/17.