the formula I am using is as follows:
=IF(29.99>=G21,G21*(5.25/100),IF(599.99>=G21,(((G21-29.99)*(3.25/100))+1.57),(((G21-99.99)*(1.75/100))+(1.57+18.53))))
I have formated the cell to 'currency', but another formuala in another cell uses the answer... the answer is not to two decimal places...