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 $62.81   8.305%   $68.0264   $68.03   $68.05   $68.00  
  Purchase #2 $234.59   8.378%   $254.244   $254.24   $254.25   $254.20  
  Purchase #3 $132.62   7.278%   $142.2721   $142.27   $142.25   $142.30  
  Purchase #4 $187.99   11.461%   $209.5355   $209.54   $209.55   $209.50  
  Purchase #5 $114.38   8.620%   $124.2396   $124.24   $124.25   $124.20  
  Purchase #6 $115.41   8.109%   $124.7686   $124.77   $124.75   $124.80  
  Purchase #7 $97.95   10.806%   $108.5345   $108.53   $108.55   $108.50  
  7 purchase totals = $945.75       $1,031.6207   $1,031.62   $1,031.65   $1,031.50