The OP's profile doesn't indicate where she lives, so the previous advice about prescriptions may or may not be of any use.

In Ontario, pharmacies are prohibited from awarding loyalty points (Shoppers Optimum, Air Miles, PC Points, etc.) on the value of prescription medicines.

I only belong to Air Miles because it's free. I fill up at Shell because the BMO premium cash back Mastercard includes roadside assistance for annual fee less than major programs charge as a stand alone and then the card throws in the 3% off fuel purchases. I shop at Metro (formerly Dominion) because it's the most convenient for me, which gets me Air Miles, but I shop at Shoppers Drug Mart instead of Pharma Plus, because it's more convenient (and generally has better selection).