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 $195.81   3.116%   $201.9114   $201.91   $201.90   $201.90  
  Purchase #2 $162.38   8.298%   $175.8543   $175.85   $175.85   $175.90  
  Purchase #3 $14.63   5.300%   $15.4054   $15.41   $15.40   $15.40  
  Purchase #4 $229.93   5.725%   $243.0935   $243.09   $243.10   $243.10  
  Purchase #5 $76.76   9.853%   $84.3232   $84.32   $84.30   $84.30  
  Purchase #6 $16.36   9.289%   $17.8797   $17.88   $17.90   $17.90  
  Purchase #7 $50.69   11.436%   $56.4869   $56.49   $56.50   $56.50  
  7 purchase totals = $746.56       $794.9544   $794.95   $794.95   $795.00