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 $88.79   5.165%   $93.376   $93.38   $93.40   $93.40  
  Purchase #2 $183.93   10.580%   $203.3898   $203.39   $203.40   $203.40  
  Purchase #3 $51.69   7.531%   $55.5828   $55.58   $55.60   $55.60  
  Purchase #4 $145.80   12.622%   $164.2029   $164.20   $164.20   $164.20  
  Purchase #5 $73.50   4.599%   $76.8803   $76.88   $76.90   $76.90  
  Purchase #6 $133.95   9.134%   $146.185   $146.19   $146.20   $146.20  
  Purchase #7 $207.73   9.588%   $227.6472   $227.65   $227.65   $227.60  
  7 purchase totals = $885.39       $967.2640   $967.27   $967.35   $967.30