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 $162.41   8.739%   $176.603   $176.60   $176.60   $176.60  
  Purchase #2 $168.63   11.690%   $188.3428   $188.34   $188.35   $188.30  
  Purchase #3 $180.41   3.211%   $186.203   $186.20   $186.20   $186.20  
  Purchase #4 $108.28   5.749%   $114.505   $114.51   $114.50   $114.50  
  Purchase #5 $20.78   12.750%   $23.4295   $23.43   $23.45   $23.40  
  Purchase #6 $98.94   5.509%   $104.3906   $104.39   $104.40   $104.40  
  Purchase #7 $212.71   13.328%   $241.06   $241.06   $241.05   $241.10  
  7 purchase totals = $952.16       $1,034.5339   $1,034.53   $1,034.55   $1,034.50