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 $68.63   4.669%   $71.8343   $71.83   $71.85   $71.80  
  Purchase #2 $243.91   3.392%   $252.1834   $252.18   $252.20   $252.20  
  Purchase #3 $195.35   6.838%   $208.708   $208.71   $208.70   $208.70  
  Purchase #4 $226.35   10.164%   $249.3562   $249.36   $249.35   $249.40  
  Purchase #5 $69.25   9.755%   $76.0053   $76.01   $76.00   $76.00  
  Purchase #6 $109.54   5.724%   $115.8101   $115.81   $115.80   $115.80  
  Purchase #7 $214.94   9.177%   $234.665   $234.67   $234.65   $234.70  
  7 purchase totals = $1,127.97       $1,208.5623   $1,208.57   $1,208.55   $1,208.60