Learn to cook and learn about nutrition, then read labels for content. Good for your budget and your body. There are other cycles as well. Keep a running total as you shop and keep track at checkout. Everybody makes mistakes.
Some markets give a discount if an item is rung incorrectly.
Take advantage of what each store has to offer. You save at both. Buy generic or store brands on basic items like flour, sugar, salt,bleach, ammonia and vinegar. But in bulk if you use the product and have the space. At some stores you can buy bulk items from bins.