That is a tough one, but I can see it’s importance.
I tackled this a few yeards ago for Quebec. They have a rule where in cases where the employee’s deductions exceeded their gross pay (tipped employees, generally) then the payroll must reduce Quebec tax, QPP, EI, and Federal tax (not necessarily in that order) until the net cheque reaches 0.00.
This was difficult, because you have to recalculate the taxes as you are doing it (QPP & EI are factors in the Federal tax calc.) but it worked.
I would be reluctant to open the hood of the DOS payroll to attempt this – my time would be better spent adding it to the NV2 payroll (IMHO).