I'd never tip in China. "Rounding up" for services like a barber is fine (say, it costs 15 RMB, I'll give 20 RMB and they'll happily accept)
Taxi drivers (if you're not using Didi) also don't mind a tip.
I'd NOT tip hotel staff, restaurant staff etc., and pay the exact amount. It's short of an insult to tip in restaurants.
IF you've liked a service extremely (a tour guide might fall on this) they might be OK with a tip, but it's far from expected.
Luckily, the crazy north american tipping doesn't exist in China (or, actually, in the rest of the world.. albeit in some countries tipping is allowed, it's nowhere mandatory) - you pay whats stated, and don't have to add like 20% to the bill.