By the time Prince William became a county in 1730 (Old Style), the colonists in Virginia had acquired the power to control taxes for support of their colonial government. The process evolved through constant tension between the King (through his appointed colonial governors) and the colonists (through their elected House of Burgesses).
You can't escape death and taxes... but the colonists in Virginia paid taxes differently than we do today. Local taxes (in addition to those established by the House of Burgesses) were imposed separately by the county court and by the church, though all were collected by the county sheriff.
The leaders (the "vestry") of the local Anglican church set a tax rate annually to cover costs of local welfare (mostly orphans, and the sick and elderly without families to support them) and church operations (especially construction of new buildings, like Pohick Church). Many members of the vestry were also justices on the county court, so the two bodies were familiar with each other's plans to raise or lower taxes.
(After the American Revolution, the new Commonwealth of Virginia "disestablished" the Anglican Church when the General Assembly passed Thomas Jefferson's Virginia Statute for Religious Freedom. The Revolutionary War in 1775-83 did not start - or stop - the constant debates regarding the appropriate level of taxation or the best way to fund services to citizens...)
The revenues for running the colonial Virginia government came primarily from port duties on ships trading in Virginia, a head tax on all imported passengers, a 2-shilling export fee on all hogsheads of tobacco shipped to England, fees associated with grants of land, fines and forfeitures, a land tax, and a poll tax on "titheables."
What's a titheable? The Library of Virginia, as part of its excellent discussion list on Virginia History, has posted some explanatory VA-Notes - including one explaining the definition of a titheable who was taxed in the colonial era.
There was a running discussion in August, 1996 on the definition of titheables, with one in particular discussing Prince William taxes at the time of the French and Indian War.
Charles Hamrick concluded that, when troops were being raised, the tax burden in Prince William was:
1759 8s/8d (8 shillings, 8 pence)
1760 73lb.Tob'o + 4s (73 pounds of tobacco plus 4 shillings)
1761 88lb.Tob'o + 4s
1762 125lb.Tob'o + 6s
Note: There were 12 pence in a shilling, and 20 shillings in the [£] pound sterling. An average Virginia "planter" with 100 acres and some family/servant/slave help (as opposed to the wealthy gentry with far more land and slave labor to work it) would produce 1000-1500 pounds of tobacco annually.
If you assume tobacco was 2d per pound, then the tax rate in Prince William County would be:
1759 - 104 pounds tobacco/1250 pounds per annual crop = 8.3% tax rate
1760 - 121 pounds tobacco/1250 pounds per annual crop = 9.7% tax rate
1761 - 136 pounds tobacco/1250 pounds per annual crop = 10.9% tax rate
1762 - 173 pounds tobacco/1250 pounds per annual crop = 13.9% tax rate
So are you surprised that the French and Indian War in the mid-1700's caused taxes to rise dramatically - up 67% in three years from 8.3% to 13.9% - in Prince William County?