Roman citizens paid no taxes, at least not necessarily. Roman state revenue was divided into the vectigals and tribute. Tribute was, by the late Republic, levied only on provincials, and it constituted by far the majority of state revenues. The vectigals included a number of duties, most of which were some sort of customs duties (the portoria) or rents on the ager publicus. With the exception of the inheritance tax the vectigals could therefore be levied on either citizens or non-citizens--but citizens did not necessarily do anything that would incur payment of such a duty. More on this here