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 $245.38   10.553%   $271.275   $271.28   $271.30   $271.30  
  Purchase #2 $142.73   10.405%   $157.5811   $157.58   $157.60   $157.60  
  Purchase #3 $78.64   7.112%   $84.2329   $84.23   $84.25   $84.20  
  Purchase #4 $43.83   5.445%   $46.2165   $46.22   $46.20   $46.20  
  Purchase #5 $105.92   7.622%   $113.9932   $113.99   $114.00   $114.00  
  Purchase #6 $213.61   10.196%   $235.3897   $235.39   $235.40   $235.40  
  Purchase #7 $130.55   10.255%   $143.9379   $143.94   $143.95   $143.90  
  7 purchase totals = $960.66       $1,052.6263   $1,052.63   $1,052.70   $1,052.60