TIL
During the times of Augustus and Tiberius, Romans paid 1% sales tax to support the empire's military expenditures.
When the people of Rome asked for a remission of the one per cent. tax on all saleable commodities, Tiberius declared by edict "that the military exchequer depended on that branch of revenue, and, further, that the State was unequal to the burden, unless the twentieth year of service were to be that of the veteran's discharge.
http://classics.mit.edu/Tacitus/annals.mb.txt
When the people of Rome asked for a remission of the one per cent. tax on all saleable commodities, Tiberius declared by edict "that the military exchequer depended on that branch of revenue, and, further, that the State was unequal to the burden, unless the twentieth year of service were to be that of the veteran's discharge.
http://classics.mit.edu/Tacitus/annals.mb.txt