Why Is Gas Priced In Tenths, Ex. $2.9990/gallon.

I just randomly wondered, why is gas priced in tenths? For example, regular is $2.9990. Apparently this is quite a mystery! One possible explanation is that gas used to cost a few pennies. This caused gas stations to really hesitate moving up to the next cent. Read more here. Another has to do with being unable to get a perfect gallon measurement, thus the difference. Check out this article, it's amazingly detailed. I'll admit I didn't read the whole thing...it was just too much info. Cliff notes please. Another reason could be that it just looks cheaper...marketting. Whatever the reason, it's kind of odd. If they rounded down, I would like to buy $0.0049 worth of gas please...4000 times. :)