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 $193.45   11.477%   $215.6523   $215.65   $215.65   $215.70  
  Purchase #2 $247.99   8.244%   $268.4343   $268.43   $268.45   $268.40  
  Purchase #3 $93.32   3.398%   $96.491   $96.49   $96.50   $96.50  
  Purchase #4 $42.38   11.448%   $47.2317   $47.23   $47.25   $47.20  
  Purchase #5 $187.98   13.788%   $213.8987   $213.90   $213.90   $213.90  
  Purchase #6 $34.86   5.172%   $36.663   $36.66   $36.65   $36.70  
  Purchase #7 $68.74   7.683%   $74.0213   $74.02   $74.00   $74.00  
  7 purchase totals = $868.72       $952.3923   $952.38   $952.40   $952.40