How much to tip airport shuttle?

[Free4Life11]

I am taking a shuttle to the airport 50 miles away from me. It is $79.99 round trip. I am wondering how much to tip. They are picking me up from a hotel I live nearby (it's $5 more for a home pickup). I am wondering how much I should tip the driver. I was thinking $10 each way. Would that be sufficient? Too much? Thanks for your help!

 

[byoung]

$10 will be find.