Originally Posted by CanadaDH

Just because they sell groceries doesn't mean they're classed as a grocery store by Amex or Visa. Walmart has a full size grocery store inside their stores, but they're not classed as grocery.

I think the easiest thing to do, is to just go there and make a purchase using your card. If it's Amex, you'll know for sure within a day or two when you see the transaction post online.

I've seen situations where different parts of the store are classed differently by Amex. For example, my local Shoppers Drug Mart posts as 2X points at the main checkout, the pharmacy checkout and the cosmetic checkout. However, if the charge is done at the Canada Post terminal, it goes through at 1X.