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 $108.69   5.156%   $114.2941   $114.29   $114.30   $114.30  
  Purchase #2 $195.44   6.531%   $208.2042   $208.20   $208.20   $208.20  
  Purchase #3 $44.44   4.380%   $46.3865   $46.39   $46.40   $46.40  
  Purchase #4 $5.38   6.130%   $5.7098   $5.71   $5.70   $5.70  
  Purchase #5 $236.37   9.524%   $258.8819   $258.88   $258.90   $258.90  
  Purchase #6 $69.25   12.602%   $77.9769   $77.98   $78.00   $78.00  
  Purchase #7 $244.82   3.713%   $253.9102   $253.91   $253.90   $253.90  
  7 purchase totals = $904.39       $965.3636   $965.36   $965.40   $965.40