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 $119.92   10.352%   $132.3341   $132.33   $132.35   $132.30  
  Purchase #2 $54.38   7.479%   $58.4471   $58.45   $58.45   $58.40  
  Purchase #3 $83.68   12.695%   $94.3032   $94.30   $94.30   $94.30  
  Purchase #4 $107.83   6.215%   $114.5316   $114.53   $114.55   $114.50  
  Purchase #5 $153.59   9.853%   $168.7232   $168.72   $168.70   $168.70  
  Purchase #6 $176.91   4.612%   $185.0691   $185.07   $185.05   $185.10  
  Purchase #7 $200.90   7.171%   $215.3065   $215.31   $215.30   $215.30  
  7 purchase totals = $897.21       $968.7148   $968.71   $968.70   $968.60