I have a few different grocery stores in my general vicinity and I decided to figure out which one was the cheapest. I chose 5 different foods that I use frequently in our household, bought them at each store and came up with the totals to see which store on average saves me the most money.
I tried to buy things that wouldn't have weight variance, so I didn't get anything like chicken or steak where the exact weight would be hard to match at every store exactly. Also I bought the cheapest version of a product. For instance if there were 2 brands of 2% milk, I would always choose the cheapest in each store. Last, I used a discount card at every store that accepted them.
Here is the result in dollar total for each of the stores I went to:
Two things I need to note are the bread at QFC and Walmart only came in a large size loaf for sourdough. Also my wife and I both noticed the quality of the milk from Walmart was not up to par with the other stores. Also Walmart only had Cheerios in a smaller size than the other stores.
To put this into perspective, spending $100.00 at Winco will get me the same as spending $126.29 at Walmart, $145 at QFC, $125.03 at Haagen and $130.68 at Safeway. Lets say we go to the grocery store about 4 times a month that 100 turns into 400 for Winco and 580. That's $2160.00 a year you're saving by choosing the right grocery store to shop at.
If you don't have these same stores in your area which is very likely, I'd recommend doing a little experiment like this to see how much you can save.