Of course, American Dollars did not exist back at the turn of the 17th Century. British colonies tended to use the Pound Sterling along with Spanish and French denominations.
In 1645 the legislature of Virginia... established the Spanish Dollar, or "piece of eight," at six Shillings, as the standard of currency for that colony. In 1655 the "piece of eight" was changed from six Shillings to five Shillings Sterling as the standard of currency.
Other colonies/states had different rates for the Spanish Dollar to Shilling conversion.
http://en.wikipedia.org/wiki/Continental_curre ncy
The Spanish Dollar later morphed into Continental Currency, which was itself replaced by the US Dollar at a rate of 1000 Continental Dollars = 1 US Dollar.
From 1526 the Crown was set at five Shillings. Thus, in the case of Virginia, 1 Dollar = 1 Crown.