How much withholding taxes did slaves pay in 1861?
They didn't; there was no direct [income] taxes (that came with the 16th amendment).
But witholdings are particularly sinister: they are either theft of what is the employer's (if the wage unpaid is still the owners), or presupposes that the fruit of your labor is foremost the government's and then yours, if the wages are really the employee's at that point. In the latter case the government has made itself equal to God, who had the right to the firstfruits under Mosaic law.