Right now you only pay for those roads with the tax on fuels.  
Tourist will not be paying the sales tax on more than cursory purchases.  They will not be paying it on the cost of airline tickets or cruise cost.  The two biggest expenses for most tourist.  They will not be paying sales tax on the meals the eat on board the ships or on the meals the eat on those ships.  So generally it will be the trinkets and bears they buy will be taxable.