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 $48.91   6.330%   $52.006   $52.01   $52.00   $52.00  
  Purchase #2 $127.52   6.857%   $136.264   $136.26   $136.25   $136.30  
  Purchase #3 $85.28   11.725%   $95.2791   $95.28   $95.30   $95.30  
  Purchase #4 $241.83   8.259%   $261.8027   $261.80   $261.80   $261.80  
  Purchase #5 $229.75   6.419%   $244.4977   $244.50   $244.50   $244.50  
  Purchase #6 $72.26   8.156%   $78.1535   $78.15   $78.15   $78.20  
  Purchase #7 $223.26   11.846%   $249.7074   $249.71   $249.70   $249.70  
  7 purchase totals = $1,028.81       $1,117.7104   $1,117.71   $1,117.70   $1,117.80