I worked for a grocery store chain for 16 years and I did the tags and pricing. It depends on each store's "formula" and that is a closely held corporate formula. But it depends on each stores "zone". Part of the formula is what competition is nearby as well as other things. The last store I worked at, there was also another store literally across the bridge from my store and the 2 were in different zones. It was a headache because I was always being called up front to explain to customers why the price of something was different at my store vs. the store down the street. I finally quit because I was tired of the 20 hour day on price change day. Oh and by the way these store cards are rip offs, you don't save as much as it appears and about 2 weeks before an item went BOGO I would get a price increase, then 2 weeks after it would go back down. Some weeks I changed 10,000 tags so there is no way customers can keep up with the true price. You might remember a few on the items you buy all the time but there is no way you could remember everything.