It's not doubling the amount of taxes necessarily. What is deducted from the employee's check can be different taxes from what the employer might have to pay in addition to that.
Except that no one can tell you exactly what those are unless we know what country you're in -- we get worldwide people around here.
If you're in the U.S. I can answer that. Social security and medicare are "matched" by the employer. That is, whatever is deducted from the paycheck of the employee is duplicated by the employer. So that one is doubled. Any federal, state or local withholdings are deductions only. Federal unemployment is employer-paid only. State unemployment may be a deduction and paid by the employer, possibly at two different percents. State stuff is always state-dependent. (Some states don't even have unemployment.) Things like Workers Comp (worker injury insurance) is employer only.