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 $67.43   3.449%   $69.7557   $69.76   $69.75   $69.80  
  Purchase #2 $141.94   4.689%   $148.5956   $148.60   $148.60   $148.60  
  Purchase #3 $152.60   5.576%   $161.109   $161.11   $161.10   $161.10  
  Purchase #4 $37.74   6.537%   $40.2071   $40.21   $40.20   $40.20  
  Purchase #5 $71.59   4.242%   $74.6268   $74.63   $74.65   $74.60  
  Purchase #6 $229.83   13.478%   $260.8065   $260.81   $260.80   $260.80  
  Purchase #7 $190.59   5.408%   $200.8971   $200.90   $200.90   $200.90  
  7 purchase totals = $891.72       $955.9978   $956.02   $956.00   $956.00