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 $196.75   6.708%   $209.948   $209.95   $209.95   $209.90  
  Purchase #2 $76.71   9.647%   $84.1102   $84.11   $84.10   $84.10  
  Purchase #3 $237.83   13.217%   $269.264   $269.26   $269.25   $269.30  
  Purchase #4 $32.68   5.247%   $34.3947   $34.39   $34.40   $34.40  
  Purchase #5 $62.69   8.517%   $68.0293   $68.03   $68.05   $68.00  
  Purchase #6 $66.60   9.458%   $72.899   $72.90   $72.90   $72.90  
  Purchase #7 $193.35   12.699%   $217.9035   $217.90   $217.90   $217.90  
  7 purchase totals = $866.61       $956.5487   $956.54   $956.55   $956.50