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 $241.63   8.207%   $261.4606   $261.46   $261.45   $261.50  
  Purchase #2 $31.76   9.127%   $34.6587   $34.66   $34.65   $34.70  
  Purchase #3 $130.49   4.451%   $136.2981   $136.30   $136.30   $136.30  
  Purchase #4 $246.29   6.507%   $262.3161   $262.32   $262.30   $262.30  
  Purchase #5 $102.96   11.114%   $114.403   $114.40   $114.40   $114.40  
  Purchase #6 $220.86   4.461%   $230.7126   $230.71   $230.70   $230.70  
  Purchase #7 $73.59   3.792%   $76.3805   $76.38   $76.40   $76.40  
  7 purchase totals = $1,047.58       $1,116.2296   $1,116.23   $1,116.20   $1,116.30