Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $32.26   10.794%   $35.7421   $35.74   $35.75   $35.70  
  Purchase #2 $232.45   10.563%   $257.0037   $257.00   $257.00   $257.00  
  Purchase #3 $16.37   7.695%   $17.6297   $17.63   $17.65   $17.60  
  Purchase #4 $242.97   3.556%   $251.61   $251.61   $251.60   $251.60  
  Purchase #5 $78.44   4.860%   $82.2522   $82.25   $82.25   $82.30  
  Purchase #6 $27.66   4.208%   $28.8239   $28.82   $28.80   $28.80  
  Purchase #7 $47.49   7.756%   $51.1733   $51.17   $51.15   $51.20  
  7 purchase totals = $677.64       $724.2349   $724.22   $724.20   $724.20