You can usually find the same items on sale in the US for a lower price, even when sales tax is taken into account. Not everything in the store will be on sale. Sale prices are usually advertised in the Sunday newspaper. The Christmas shopping season officially starts the Friday after Thanksgiving, but some stores will offer sales starting the weekend before Thanksgiving. If you don't need something immediately, it is best to wait until it is on sale.
Supermarkets are large grocery stores, often part of a chain of stores.
It is generally less expensive to shop in a supermarket than in a small local grocery, and the selection is larger. The major grocery store chains advertise their sale prices in circulars that are distributed by mail toward the end of the week, and sometimes as an insert in the Sunday newspaper. The Sunday newspaper will also include collections of manufacturer cents-off coupons which you can clip and give to the cashier to save on purchases. Some supermarkets will double the value of manufacturer coupons. For non-perishable goods, it is worthwhile to stock up when the item goes on sale.