system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why are gas prices typically the only thing we sell to the $0.009? When and why did this start? If it's only supposed to be effective marketing then why do other products not use it?
gpt
It started because of taxes. Back when gas only cost about 0.15/gallon the federal government decided they wanted a piece of that to build and maintain roads, so they enacted a 3/10 of a cent tax. Gas companies weren't about to eat that so they passed the cost along to customers. Since gas was only 15 cents, rounding up a whole penny would be too much and would drive customers to your competitor.

Eventually they noticed that people didn't round up. If you price something at 49.9 cents, people treat it like it's 49 cents, not 50. That's why damn near everything is priced like that. 2.99, 14,990, etc. So they get to pocket almost an entire cent per gallon that people don't even feel like they're paying.