Are we talking about tipping the person who pays you or do you really mean your host?
I give my host nothing when I hit a taxable handpay.
If you are talking about tips for the person who pays you, then you might want to search the archives since there has been substantial discussion on this in the past. I think there was also a poll and the results may still be around.
http://search.msn.com/results.aspx?q=weather&FORM=WLMTAG
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