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 $41.29   7.266%   $44.2901   $44.29   $44.30   $44.30  
  Purchase #2 $153.71   13.638%   $174.673   $174.67   $174.65   $174.70  
  Purchase #3 $71.25   10.174%   $78.499   $78.50   $78.50   $78.50  
  Purchase #4 $43.84   13.354%   $49.6944   $49.69   $49.70   $49.70  
  Purchase #5 $102.49   13.369%   $116.1919   $116.19   $116.20   $116.20  
  Purchase #6 $187.73   5.692%   $198.4156   $198.42   $198.40   $198.40  
  Purchase #7 $237.64   10.630%   $262.9011   $262.90   $262.90   $262.90  
  7 purchase totals = $837.95       $924.6651   $924.66   $924.65   $924.70