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 $208.71   8.553%   $226.561   $226.56   $226.55   $226.60  
  Purchase #2 $69.41   11.305%   $77.2568   $77.26   $77.25   $77.30  
  Purchase #3 $135.55   4.383%   $141.4912   $141.49   $141.50   $141.50  
  Purchase #4 $212.57   13.589%   $241.4561   $241.46   $241.45   $241.50  
  Purchase #5 $21.44   6.202%   $22.7697   $22.77   $22.75   $22.80  
  Purchase #6 $214.49   5.388%   $226.0467   $226.05   $226.05   $226.00  
  Purchase #7 $72.54   8.472%   $78.6856   $78.69   $78.70   $78.70  
  7 purchase totals = $934.71       $1,014.2671   $1,014.28   $1,014.25   $1,014.40