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 $225.79   9.684%   $247.6555   $247.66   $247.65   $247.70  
  Purchase #2 $221.84   3.547%   $229.7087   $229.71   $229.70   $229.70  
  Purchase #3 $209.62   4.544%   $219.1451   $219.15   $219.15   $219.10  
  Purchase #4 $236.47   10.721%   $261.8219   $261.82   $261.80   $261.80  
  Purchase #5 $236.79   10.743%   $262.2283   $262.23   $262.25   $262.20  
  Purchase #6 $236.25   4.429%   $246.7135   $246.71   $246.70   $246.70  
  Purchase #7 $26.80   5.111%   $28.1697   $28.17   $28.15   $28.20  
  7 purchase totals = $1,393.56       $1,495.4427   $1,495.45   $1,495.40   $1,495.40