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 $58.48   6.697%   $62.3964   $62.40   $62.40   $62.40  
  Purchase #2 $246.53   3.697%   $255.6442   $255.64   $255.65   $255.60  
  Purchase #3 $81.52   3.587%   $84.4441   $84.44   $84.45   $84.40  
  Purchase #4 $201.53   3.439%   $208.4606   $208.46   $208.45   $208.50  
  Purchase #5 $90.75   12.162%   $101.787   $101.79   $101.80   $101.80  
  Purchase #6 $130.65   3.649%   $135.4174   $135.42   $135.40   $135.40  
  Purchase #7 $30.73   11.521%   $34.2704   $34.27   $34.25   $34.30  
  7 purchase totals = $840.19       $882.4201   $882.42   $882.40   $882.40