Yes, below find the solution that helped me to solve the problem.

def _compute_all_tax(self):
"""
As the taxes are recalculated based on a single discount, we need to
simulate a multiple discount by changing discount value. Values are
restored after the original process is done
"""
digits = self._fields["discount"]._digits
self._fields["discount"]._digits = (16, 2) # This is added to avoid errors and adding a lot of zero's after comma