All month the foodie website, Epicurious, is talking about the different ways in which we grocery shop. As a test, editors shopped for staple food items at five different stores, to see which was the cheapest. Among the contenders: Whole Foods, Trader Joe's, Costco, Peapod and a standard supermarket. David Tamarkin, editor of Epicurious, joins Your Cheddar to reveal which chains are the cheapest, and which you should avoid to keep your wallet happy.