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 $182.63   6.713%   $194.89   $194.89   $194.90   $194.90  
  Purchase #2 $91.38   4.145%   $95.1677   $95.17   $95.15   $95.20  
  Purchase #3 $14.32   13.247%   $16.217   $16.22   $16.20   $16.20  
  Purchase #4 $188.94   3.509%   $195.5699   $195.57   $195.55   $195.60  
  Purchase #5 $180.51   12.714%   $203.46   $203.46   $203.45   $203.50  
  Purchase #6 $61.81   13.662%   $70.2545   $70.25   $70.25   $70.30  
  Purchase #7 $159.58   11.138%   $177.354   $177.35   $177.35   $177.40  
  7 purchase totals = $879.17       $952.9131   $952.91   $952.85   $953.10