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 $114.38   9.558%   $125.3124   $125.31   $125.30   $125.30  
  Purchase #2 $231.79   5.227%   $243.9057   $243.91   $243.90   $243.90  
  Purchase #3 $58.86   13.725%   $66.9385   $66.94   $66.95   $66.90  
  Purchase #4 $73.57   3.647%   $76.2531   $76.25   $76.25   $76.30  
  Purchase #5 $169.73   13.204%   $192.1411   $192.14   $192.15   $192.10  
  Purchase #6 $151.99   11.613%   $169.6406   $169.64   $169.65   $169.60  
  Purchase #7 $158.41   12.326%   $177.9356   $177.94   $177.95   $177.90  
  7 purchase totals = $958.73       $1,052.1270   $1,052.13   $1,052.15   $1,052.00