"Tip" as such isn't included in Austria, or most European countries. Service fee, however, is included in the menu prices. Rounding up a bill is polite, and also convenient for the guest and waiter, with no need to handle small change.
Except for some Asian countries, where everything over the bill price is refused, there is of course nothing illegal to be more generous when rounding up, if you have been very happy with the service provided