Taxes are never correct on Hertz.com. They always overestimate. For that matter, Priceline doesn't get all the fees correct either. I had a one-way normal reservation on Priceline a few years back that did not include a drop fee but it was on the reservation at the counter. Had a nice battle over that one...
As long as it isn't a "Name Your Own Price" bidding car rental reservation, you'll get credit.
If the prices are the same (and it isn't a pre-pay), I'd use Hertz.com.