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 $237.28   10.673%   $262.6049   $262.60   $262.60   $262.60  
  Purchase #2 $48.61   3.827%   $50.4703   $50.47   $50.45   $50.50  
  Purchase #3 $208.47   12.219%   $233.9429   $233.94   $233.95   $233.90  
  Purchase #4 $96.85   5.143%   $101.831   $101.83   $101.85   $101.80  
  Purchase #5 $97.26   4.834%   $101.9615   $101.96   $101.95   $102.00  
  Purchase #6 $34.38   4.856%   $36.0495   $36.05   $36.05   $36.00  
  Purchase #7 $245.25   10.433%   $270.8369   $270.84   $270.85   $270.80  
  7 purchase totals = $968.10       $1,057.6970   $1,057.69   $1,057.70   $1,057.60