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 $197.66   5.587%   $208.7033   $208.70   $208.70   $208.70  
  Purchase #2 $187.53   12.655%   $211.2619   $211.26   $211.25   $211.30  
  Purchase #3 $40.88   3.327%   $42.2401   $42.24   $42.25   $42.20  
  Purchase #4 $112.75   10.643%   $124.75   $124.75   $124.75   $124.80  
  Purchase #5 $124.49   11.866%   $139.262   $139.26   $139.25   $139.30  
  Purchase #6 $226.25   8.509%   $245.5016   $245.50   $245.50   $245.50  
  Purchase #7 $74.81   11.183%   $83.176   $83.18   $83.20   $83.20  
  7 purchase totals = $964.37       $1,054.8949   $1,054.89   $1,054.90   $1,055.00