Why are per gallon gasoline prices at the pump always end in 9/10's of a cent?

This is just a ridiculous tradition to let you believe you are paying less than you really are. It is like the prices for other kinds of merchandise are often at price points like $0.99, $9.99, $49.99, $99.99, etc. You are essentially paying a hundred bucks, but your mind is seeing the price as "less than a hundred bucks."

There are studies that indicate that significantly more products sell when they have this kind of pricing.

So imagine there are two gas stations across the street from each other. One has a price sign out that says $3.79 and the other has a price sign that says $3.78 and then after the 8 there is a very tiny 9, making the actual price $3.789. The second station will get the majority of the customers while earning virtually the same profit margin. So all the stations price this way to compete.

It's due to taxes....some only collect part in partial cents.

for some reason people think its cheaper than the round number.