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 $88.42   6.450%   $94.1231   $94.12   $94.10   $94.10  
  Purchase #2 $131.75   7.548%   $141.6945   $141.69   $141.70   $141.70  
  Purchase #3 $236.63   10.680%   $261.9021   $261.90   $261.90   $261.90  
  Purchase #4 $60.53   3.547%   $62.677   $62.68   $62.70   $62.70  
  Purchase #5 $169.47   5.507%   $178.8027   $178.80   $178.80   $178.80  
  Purchase #6 $188.87   12.632%   $212.7281   $212.73   $212.75   $212.70  
  Purchase #7 $249.70   3.803%   $259.1961   $259.20   $259.20   $259.20  
  7 purchase totals = $1,125.37       $1,211.1236   $1,211.12   $1,211.15   $1,211.10