The norm
Tipping is not expected in Cyprus the way it is in the United States. Drivers are not paid a sub-minimum wage on the assumption that you will top it up. The fare is the fare.
When people do
Rounding up is common and appreciated — €85 becomes €90, that sort of thing. If a driver has genuinely gone out of his way (carried your cases up three flights, waited an hour for a delayed bag, driven at 4am on a public holiday), a tip lands well. It is a thank-you, not a wage.
What matters more
Honestly? Book the same driver again. That is worth more to a one-man operation than a fiver, and it is worth more to you too — because the second time, he already knows where you live.