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 $232.94   12.368%   $261.75   $261.75   $261.75   $261.80  
  Purchase #2 $200.65   3.227%   $207.125   $207.13   $207.15   $207.10  
  Purchase #3 $124.95   4.533%   $130.614   $130.61   $130.60   $130.60  
  Purchase #4 $42.39   6.715%   $45.2365   $45.24   $45.25   $45.20  
  Purchase #5 $192.53   4.135%   $200.4911   $200.49   $200.50   $200.50  
  Purchase #6 $79.89   3.398%   $82.6047   $82.60   $82.60   $82.60  
  Purchase #7 $33.35   4.141%   $34.731   $34.73   $34.75   $34.70  
  7 purchase totals = $906.70       $962.5523   $962.55   $962.60   $962.50