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 $69.26   9.357%   $75.7407   $75.74   $75.75   $75.70  
  Purchase #2 $224.67   13.680%   $255.4049   $255.40   $255.40   $255.40  
  Purchase #3 $60.70   10.749%   $67.2246   $67.22   $67.20   $67.20  
  Purchase #4 $83.73   7.196%   $89.7552   $89.76   $89.75   $89.80  
  Purchase #5 $157.95   3.309%   $163.1766   $163.18   $163.20   $163.20  
  Purchase #6 $240.90   8.522%   $261.4295   $261.43   $261.45   $261.40  
  Purchase #7 $96.49   4.839%   $101.1592   $101.16   $101.15   $101.20  
  7 purchase totals = $933.70       $1,013.8907   $1,013.89   $1,013.90   $1,013.90