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 $84.76   13.230%   $95.9737   $95.97   $95.95   $96.00  
  Purchase #2 $25.56   5.669%   $27.009   $27.01   $27.00   $27.00  
  Purchase #3 $104.69   3.301%   $108.1458   $108.15   $108.15   $108.10  
  Purchase #4 $45.72   4.834%   $47.9301   $47.93   $47.95   $47.90  
  Purchase #5 $158.43   4.528%   $165.6037   $165.60   $165.60   $165.60  
  Purchase #6 $27.43   3.504%   $28.3911   $28.39   $28.40   $28.40  
  Purchase #7 $236.31   11.808%   $264.2135   $264.21   $264.20   $264.20  
  7 purchase totals = $682.90       $737.2669   $737.26   $737.25   $737.20