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 $173.27   12.874%   $195.5768   $195.58   $195.60   $195.60  
  Purchase #2 $105.89   6.339%   $112.6024   $112.60   $112.60   $112.60  
  Purchase #3 $155.74   13.161%   $176.2369   $176.24   $176.25   $176.20  
  Purchase #4 $209.93   3.403%   $217.0739   $217.07   $217.05   $217.10  
  Purchase #5 $125.92   5.383%   $132.6983   $132.70   $132.70   $132.70  
  Purchase #6 $52.35   13.425%   $59.378   $59.38   $59.40   $59.40  
  Purchase #7 $57.62   12.181%   $64.6387   $64.64   $64.65   $64.60  
  7 purchase totals = $880.72       $958.2050   $958.21   $958.25   $958.20