(Undated) -- Six major retailers are making it easier to find good deals on their websites. Walmart, Costco, Walgreens, FreshDirect, CVS and Drugstore.com, three of which have actual stores in Canton, are all adding unit pricing to their product pages. The changes will occur over the next nine months. Unit pricing allows customers to price shop when different products are offered in different sizes. Amazon, the world's biggest online retailer, is staying away from unit pricing for now.