Here are some basic rules for CVS:
CVS uses a loyalty card. Limits are set based on card purchase. Get yourself a CVS card and use it with every transaction. This is how you earn special promotional discounts and Extra Care Bucks (ecb's).
ECB's print out at the bottom of your receipt. ECB's are like cash and can be used on anything (except the usual excluded items, alcohol, tobacco, etc). You can roll them into your next deal, including the same item (unlike Walgreens). You can buy one thing, get an ecb, turn around and use that ecb on the same thing. Since CVS uses a loyalty card system and can limit the amount of "deals" you get per card, they don't have to worry about all the catalina hijinks that Walgreens has to do with not being able to use an rr to get an rr for the same product, etc. Lately they have been adding "Limit 1"
After I do my first transaction, I tear off my ecb's from the bottom of the receipt and then use them in the next transaction- or if I'm on the last transaction, I put the ecb in my CVS envelope so I know where it is. (those receipts tend to get lost)
If you're starting out, and will be near a CVS, go ahead and stop in and get a CVS card. Register with it online and enter an email address and they will email you a $4/$20 coupon.