Did you know that you can use 1 "Store" coupon and 1 Manufacturer's coupon together on 1 item? This is called "stacking", and it's totally legit!
Walgreens, CVS, and Target are really great about this. They offer lots of store coupons in booklets, in their ads, on receipts, online, and more.
In the event that you may be getting an item FREE or even earning overage on the item, make sure you give the manufacturer's coupon first. The store coupon actually adjusts the price like a sale, and it would make the manufacturer's coupon "beep" (which might make a cashier not accept it...).