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 $92.40   3.495%   $95.6294   $95.63   $95.65   $95.60  
  Purchase #2 $174.41   10.379%   $192.512   $192.51   $192.50   $192.50  
  Purchase #3 $56.28   12.801%   $63.4844   $63.48   $63.50   $63.50  
  Purchase #4 $47.54   10.562%   $52.5612   $52.56   $52.55   $52.60  
  Purchase #5 $51.61   13.867%   $58.7668   $58.77   $58.75   $58.80  
  Purchase #6 $76.69   3.201%   $79.1448   $79.14   $79.15   $79.10  
  Purchase #7 $183.59   5.642%   $193.9481   $193.95   $193.95   $193.90  
  7 purchase totals = $682.52       $736.0467   $736.04   $736.05   $736.00