You may already know that Walmart and Target will price match on many items, meaning they'll give you competitors' advertised sale prices if you show the ad at the time of purchase. Walmart has taken this concept a step further with their new Savings Catcher program, which they recently rolled out nationwide.
I generally don't try to use price matching for groceries, for many reasons. Having spent a few months checking groceries when I was in college, I empathize with the Walmart register clerk ringing up my order. She's already handled my mountain of groceries and my pile of coupons. I also have compassion for the people waiting behind me at Walmart. I hate holding up the line.
Plus, Walmart already has the lowest prices on most items. I shop at various grocery stores on a regular basis to follow the best deals. I have a good enough memory for prices on items I buy regularly to conclude that Walmart adjusts their prices based on competitors' grocery ads.
If another store has 2-liter bottles of Coke products on sale for $1, Walmart will often price them at $1. If nobody has them on sale, Walmart's price will probably hang around $1.25 to $1.50. Other stores charge about $2 for this product as a regular, non-sale price.
If another store has Chef Boyardee canned pasta products on sale for $1, Walmart might price them at 88 cents. Grocery stores sometimes put them on sale for $1.25 a can, when Walmart sells them for $1. I just bought a cantaloupe on sale at a grocery store for $3. A couple of days later, I bought two cantaloupes at Walmart for $1.49 each. You get the idea.