You pay the tax on the wholesale value anyways if the appraised value is lower, appraisal is irrelevant. If it's higher I'm sure they'd be happy to charge you tax on that value instead however.
Appraisals only really come into play with vehicle valuations when you're trying to insure a vehicle for more than its book value.
Last car I bought, paid $2500, book was for $6500. Was advised by the MTO agent to get an appraisal, which is what I ultimately payed taxes on... this was 8 months ago