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 $88.26   8.326%   $95.6085   $95.61   $95.60   $95.60  
  Purchase #2 $67.28   4.195%   $70.1024   $70.10   $70.10   $70.10  
  Purchase #3 $146.38   11.696%   $163.5006   $163.50   $163.50   $163.50  
  Purchase #4 $69.92   12.571%   $78.7096   $78.71   $78.70   $78.70  
  Purchase #5 $165.62   4.588%   $173.2186   $173.22   $173.20   $173.20  
  Purchase #6 $7.53   11.229%   $8.3755   $8.38   $8.40   $8.40  
  Purchase #7 $132.52   8.585%   $143.8968   $143.90   $143.90   $143.90  
  7 purchase totals = $677.51       $733.4120   $733.42   $733.40   $733.40