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 $213.53   6.802%   $228.0543   $228.05   $228.05   $228.10  
  Purchase #2 $187.31   3.122%   $193.1578   $193.16   $193.15   $193.20  
  Purchase #3 $40.79   9.645%   $44.7242   $44.72   $44.70   $44.70  
  Purchase #4 $76.27   6.349%   $81.1124   $81.11   $81.10   $81.10  
  Purchase #5 $249.48   10.813%   $276.4563   $276.46   $276.45   $276.50  
  Purchase #6 $116.38   13.610%   $132.2193   $132.22   $132.20   $132.20  
  Purchase #7 $242.69   3.106%   $250.228   $250.23   $250.25   $250.20  
  7 purchase totals = $1,126.45       $1,205.9523   $1,205.95   $1,205.90   $1,206.00