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 $59.55   4.167%   $62.0314   $62.03   $62.05   $62.00  
  Purchase #2 $231.31   7.189%   $247.9389   $247.94   $247.95   $247.90  
  Purchase #3 $189.78   12.517%   $213.5348   $213.53   $213.55   $213.50  
  Purchase #4 $190.80   8.328%   $206.6898   $206.69   $206.70   $206.70  
  Purchase #5 $126.81   5.766%   $134.1219   $134.12   $134.10   $134.10  
  Purchase #6 $211.38   11.854%   $236.437   $236.44   $236.45   $236.40  
  Purchase #7 $247.45   5.411%   $260.8395   $260.84   $260.85   $260.80  
  7 purchase totals = $1,257.08       $1,361.5933   $1,361.59   $1,361.65   $1,361.40