The practice of pricing fuel with a fraction of a penny is thought to have started around the 1930s. While we can’t be sure who was the first to price fuel this way, it seems to have become relatively commonplace across the United States all the sudden around the same time. So what happened? In short- taxes and the Great Depression.
Source Gizmodo http://feeds.gawker.com/~r/gizmodo/full/~3/uP9IkAGiAYQ/why-gas-is-priced-in-tenths-of-cents-1697431140
