Sushi is proving popular with shoppers at supermarkets like Kroger.Houston Chronicle/Getty Images Kroger has quietly become the biggest sushi seller in the US, The Wall Street Journal reported. America's largest grocery retailer sells more than 40 million pieces of sushi a year. Kroger wants to become a destination for more than just your groceries. Supermarket sushi is becoming a mainstay with US shoppers wanting quick, healthy, and easily transported meals.