I used to only go to Walmart since they are very close to my house. However, I've been trying to work on the couponing thing lately and have found that Walgreens can sometimes be cheaper than Walmart. We don't have a CVS here
but it looks like they may have the best deals in terms of the ECBs, though Walgreens does have their Register Rewards... However their coupon policy is a little weird in that the number of coupons must match the number of items being purchased and the RRs are counted as coupons. So sometimes in order to use all of the coupons you want, you need to buy "filler" items (eg cheap candy for a quarter, etc.) to meet the coupon policy.