system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 gas prices and how they get away with charging fractions of a penny

Gas is the only thing I ever see as being listed $3.599. How do they get away with this? I assume this is done to make their prices look cheaper but why are they allowed to do it? And even more so why does my total always wind up coming to a full cent amount? If I buy two gallons at $3.599 then my total should come to $7.198 right?
gpt
Petrol is one of the few things that you don't have to buy in units - you just pour until you have enough.  For this reason the amount that you get is rarely a whole number and so you're already dealing with fractions of pennies when it comes to the final price.  If you add into that the fact that many people have tens of gallons then it makes sense for the company to say that 1 gallon is $3.599 rather than the more obvious 10 gallons is $35.99.