Honestly? ESPECIALLY when I'm traveling, I have 99 things going on and the price of gas isn't one of them.

Between "cheap gas" and "stupidly expensive gas" you're looking at a variance in the cost of a fillup of what - $2 perhaps? Even if it's twice that, am I going to drive out of my way several blocks just to pick up a few discarded dollar bills? No. So I'm not doing that in my rental car, either.