Federal Tax accruing on vacation accrual

We just starting accruing vacation/sick time for one employee.  Upon comparing our excel calculation worksheet to what SAGE 100 calculated, the federal tax is off by about $1.50.  It is only off on the employee that started accruing benefits.  Any ideas on what needs to be done to fix this?  Prior to this starting, our excel worksheet always matched within a couple cents or so.