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 $69.25   9.256%   $75.6598   $75.66   $75.65   $75.70  
  Purchase #2 $213.42   4.199%   $222.3815   $222.38   $222.40   $222.40  
  Purchase #3 $65.90   13.254%   $74.6344   $74.63   $74.65   $74.60  
  Purchase #4 $224.56   10.763%   $248.7294   $248.73   $248.75   $248.70  
  Purchase #5 $217.69   4.157%   $226.7394   $226.74   $226.75   $226.70  
  Purchase #6 $234.49   6.250%   $249.1456   $249.15   $249.15   $249.10  
  Purchase #7 $139.26   6.541%   $148.369   $148.37   $148.35   $148.40  
  7 purchase totals = $1,164.57       $1,245.6591   $1,245.66   $1,245.70   $1,245.60