Why are prices like “$59.99” “$19.99” “$4.99” etc like I’m sure it’s probably some marketing thought suggestion shit that makes purchases seem more justifiable but I’m very curious of the actual reasoning and history behind this shit

I’m Ruby。 I’m roughly 20 apples tall
ルビーです。背がりんごを20つぐらいです。
I drew my profile pic and banner. The gameplay in the banner is from dragon quest 1 for game boy that I recorded myself.
Why are prices like “$59.99” “$19.99” “$4.99” etc like I’m sure it’s probably some marketing thought suggestion shit that makes purchases seem more justifiable but I’m very curious of the actual reasoning and history behind this shit