North Jersey's traditional supermarkets, already battling competition from discounters such as Walmart and Target, as well as new arrivals like Whole Foods, Trader Joe's and Fairway, have some new rivals nibbling at their sales - drugstores and online retailers. Drugstore chains and e-commerce giant Amazon are taking a big enough bite out of traditional grocery sales to be included on an annual industry list of the top supermarket retailers in the United States and Canada.