Towing can be expensive, but then again you don't really need a tow to mount a spare tire, plus Hertz wasn't offering towing anyway if you look at page that shows the actual coverage.

As for the taxes, yes your taxes are already included for the services that are bundled in, but any additional add-ons will also be charged at the going tax rate which will likely include:

Local Municipality Taxes
Airport Taxes
Concession Recovery Fees

All of which are charged as a percentage of your total rate, so if your total is $168 for the roadside coverage, then there can be multiple taxes/fees levied on top of that.