There is generally a dominant chain in the area which sets their price via their advisors (yes, they base it on what they think the next tank will cost). Then all the smaller market stations send out runners to check the big chains prices and they copy them or drop a 1/2 penny to bring in the blue hairs for their coffee and doughnuts
MOST gas stations do not make their money on fuel, they make it on the other crap you buy while you're in there. They tend to make the most as prices are going down, not up(I think you know why).