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 $93.65   8.369%   $101.4876   $101.49   $101.50   $101.50  
  Purchase #2 $146.70   7.366%   $157.5059   $157.51   $157.50   $157.50  
  Purchase #3 $86.86   13.120%   $98.256   $98.26   $98.25   $98.30  
  Purchase #4 $193.56   3.130%   $199.6184   $199.62   $199.60   $199.60  
  Purchase #5 $55.27   6.874%   $59.0693   $59.07   $59.05   $59.10  
  Purchase #6 $105.33   13.385%   $119.4284   $119.43   $119.45   $119.40  
  Purchase #7 $134.87   13.150%   $152.6054   $152.61   $152.60   $152.60  
  7 purchase totals = $816.24       $887.9710   $887.99   $887.95   $888.00