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 $214.53   4.697%   $224.6065   $224.61   $224.60   $224.60  
  Purchase #2 $179.86   7.635%   $193.5923   $193.59   $193.60   $193.60  
  Purchase #3 $69.64   13.433%   $78.9947   $78.99   $79.00   $79.00  
  Purchase #4 $188.51   10.636%   $208.5599   $208.56   $208.55   $208.60  
  Purchase #5 $109.57   5.540%   $115.6402   $115.64   $115.65   $115.60  
  Purchase #6 $228.78   9.477%   $250.4615   $250.46   $250.45   $250.50  
  Purchase #7 $119.36   11.501%   $133.0876   $133.09   $133.10   $133.10  
  7 purchase totals = $1,110.25       $1,204.9427   $1,204.94   $1,204.95   $1,205.00