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 $168.79   4.452%   $176.3045   $176.30   $176.30   $176.30  
  Purchase #2 $247.42   5.848%   $261.8891   $261.89   $261.90   $261.90  
  Purchase #3 $124.68   9.856%   $136.9685   $136.97   $136.95   $137.00  
  Purchase #4 $83.96   12.211%   $94.2124   $94.21   $94.20   $94.20  
  Purchase #5 $26.46   10.627%   $29.2719   $29.27   $29.25   $29.30  
  Purchase #6 $35.77   13.556%   $40.619   $40.62   $40.60   $40.60  
  Purchase #7 $14.90   12.793%   $16.8062   $16.81   $16.80   $16.80  
  7 purchase totals = $701.98       $756.0716   $756.07   $756.00   $756.10