A 2 part floor/garage epoxy will do the trick. There are a few real good choices on the market and then there are some that are ok. US Industrial Coatings http://floorepoxy.com/commercial_epoxy.htm and EpoArmor Garage Floor Epoxy http://www.garagefloor.com/garage-floor-epoxy.htm are serious ones. SW and Home Depot sell some cheaper, decent kits too. Keep in mind a tattoo shop needs to be clean/sterile/easy to clean/etc, so this may affect your paint choice as well.
The key to painting any floor is the prep. Make sure and follow the directions/dry times to the T.
The key to painting any floor is the prep. Make sure and follow the directions/dry times to the T.