Many frequent couponers have a lifelong policy: "No coupon, no purchase!" The same applies to those of us who make many of our purchases online. Sites such as RetailMeNot and apps such as dealnews can provide you with all of the applicable promo codes that will give you big discounts at your favorite websites.
In addition, some mobile payment plans like LevelUp and Zavers can give you instant rewards just for using your phone to pay rather than paying with a credit card.
Overall, it doesn't appear to matter how you make your payment or what types of rewards you use. As long as you get a discount on your purchase, you're saving money and avoiding the dreaded option of paying full price.