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 $66.76   13.664%   $75.8821   $75.88   $75.90   $75.90  
  Purchase #2 $229.36   13.357%   $259.9956   $260.00   $260.00   $260.00  
  Purchase #3 $247.70   7.565%   $266.4385   $266.44   $266.45   $266.40  
  Purchase #4 $77.62   9.799%   $85.226   $85.23   $85.25   $85.20  
  Purchase #5 $110.63   3.508%   $114.5109   $114.51   $114.50   $114.50  
  Purchase #6 $157.62   6.770%   $168.2909   $168.29   $168.30   $168.30  
  Purchase #7 $198.99   9.255%   $217.4065   $217.41   $217.40   $217.40  
  7 purchase totals = $1,088.68       $1,187.7505   $1,187.76   $1,187.80   $1,187.70