just charge tax on everything you do... the dept isnt going to complain about recieving too much money.
if you want to appear competitive, dont build tax into your prices... have a clause that states "all prices will be charged 7% OH sales tax" or the like. This also benefits you in another way. I think it was 2 years ago, tax was raised from 6 to 7%... I had about half my clients with 6% built into their rates... the other half were specified that sales tax was extra. well moral of the story, i ate the 1% on half my clients for about half a season because of how i worded it.