Many Greek hotel stays include breakfast in the room rate. A 16% service fee is included in the bill at restaurants, bars etc., but is not displayed separately. The service fee should be written on the menu - look for it towards the end, along with municipal taxes and other charges. An additional tip is is not obligatory, but it is common to round off the amount, especially when paying in cash. For example, you may choose to pay 20 Euro for a 18,60 Euro bill, if you are satisfied with the service. Such tips can be left on the table, or you may tell the server that you don't expect to be given any change.

tipping is optional keeping in mind most young waitress/waiters rely on there tips as wages can be low in greece,

 I always say... if they give good service give a good tip