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 $24.39   7.445%   $26.2058   $26.21   $26.20   $26.20  
  Purchase #2 $132.73   6.328%   $141.1292   $141.13   $141.15   $141.10  
  Purchase #3 $240.59   8.145%   $260.1861   $260.19   $260.20   $260.20  
  Purchase #4 $64.80   13.766%   $73.7204   $73.72   $73.70   $73.70  
  Purchase #5 $27.29   12.596%   $30.7274   $30.73   $30.75   $30.70  
  Purchase #6 $208.61   10.602%   $230.7268   $230.73   $230.75   $230.70  
  Purchase #7 $250.72   4.143%   $261.1073   $261.11   $261.10   $261.10  
  7 purchase totals = $949.13       $1,023.8030   $1,023.82   $1,023.85   $1,023.70