Tipping etiquette

Hey guys I just want to get some honest opinions out there… Sometimes I get my nails done and they charge me $30 +13% tax which is $33.90.. so sometimes I'll just add three bucks on top of that. Or when I get my hair done for 50 bucks plus tax… I'll just give 10 bucks… I usually do flat rates versus percentage in my opinion because I'm paying tax and the percentage is usually calculated with the tax. I do however will do the usual 15% for when I eat out or add the tax up but a little something something on top but honestly I don't really follow the percentage rule. For example if I got my hair dyed… I got quoted $275 plus tax is like 310.. let's just say I wanted to tip 15%… That's like $46… That seems a little steep for me so please tell me what your honest opinion's are… Does the average really tip that much??!?!!?!! Or do you just sometimes do flat rates like me?? Lol call me cheap .. I don't give a fuck but maybe people wouldn't rely on tips so much if they got paid decent wages. Also how the fuck are girls supposed to maintain their hair nails waxing browse every single month without going broke??