Why does the cost of gas include 9/10 cent?

Question

Why does the cost of gas include 9/10 cent?

Answer 1

taxes

Answer 2

To make it seem cheaper than it is.  It's the same thing when stores will write, "$9.99," instead of just, "$10."

Answer 3

So they can get a little more out of you. 9/10 of a penny is negligible, but it adds up.

Answer 4

because there was a time when gas was less than $1.00