I try to always run on the top half of the tank. (yeah, I've coasted into gas stations too). I try to explain to my wife how hard it is on the pump to run it dry as the pump needs to remain submerged for cooling. It doesn't cost anymore money to drive around on the lower 1/4 empty to 1/4) of a tank or the top (3/4 to full) if you drive x amount of miles and get x mpg it costs the same amount if $$$.
Not only is this better on your fuel pump, it is also better on your tank and fuel system. The less area in the tank exposed to air the less condensation you get in the tank. That's why you should always store your car with a full tank.
That being said, my car is just on the 1/2 mark so I need to run in and top it off again.