I don't see the stated problem here. Gasoline is a continuous fluid to more digits than we can actually measure with the comparatively crude instruments used in gas pumps.
He's not selling a gallon of gas for 4.009; he's selling 10/4009 gallons for a penny.
There's actually a worse problem that reached mild fame here in the US before dying away. Gas station pumps don't have the temperature correcting hardware they do everywhere else for historical reasons. The amount of gas you sell varies a couple of percent based on the temperature came out of the delivery truck (it usually doesn't sit int the tank long enough to equalize with the underground temperature--that takes weeks), and the truck's meter corrects for temperature, so the station pays for the gas temperature corrected. But the cost of the temperature correcting hardware outweighs the average consumer loss, so it doesn't get fixed (the cost of the correction would inevitably be passed onto the consumer, mostly by driving ancient rural gas stations out of business).
I suppose one could special order fuel pumps that actually do temperature correction (they do exist--Canada uses them), but the evaluation across the entire industry in the US is it would end up costing the consumer more than just eating the error. Gas stations are extremely thin margin (they tell me it's less than a penny a gallon) so the only place that money can come from is higher prices, and consumers are extremely price sensitive and bad at evaluating value. You could get a little extra popularity from advertising that you do temperature correction, but it probably won't tip the scale.
So if you care about accuracy, the 9/10 of a cent isn't the problem. The fuel volume change with temperature is.