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 $116.68   7.590%   $125.536   $125.54   $125.55   $125.50  
  Purchase #2 $149.42   12.763%   $168.4905   $168.49   $168.50   $168.50  
  Purchase #3 $106.29   10.791%   $117.7598   $117.76   $117.75   $117.80  
  Purchase #4 $86.28   7.738%   $92.9563   $92.96   $92.95   $93.00  
  Purchase #5 $221.83   13.552%   $251.8924   $251.89   $251.90   $251.90  
  Purchase #6 $69.64   9.620%   $76.3394   $76.34   $76.35   $76.30  
  Purchase #7 $136.65   11.588%   $152.485   $152.49   $152.50   $152.50  
  7 purchase totals = $886.79       $985.4594   $985.47   $985.50   $985.50