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 $32.54   9.730%   $35.7061   $35.71   $35.70   $35.70  
  Purchase #2 $242.46   4.714%   $253.8896   $253.89   $253.90   $253.90  
  Purchase #3 $72.41   9.726%   $79.4526   $79.45   $79.45   $79.50  
  Purchase #4 $234.75   3.344%   $242.6   $242.60   $242.60   $242.60  
  Purchase #5 $217.46   10.262%   $239.7757   $239.78   $239.80   $239.80  
  Purchase #6 $133.99   13.806%   $152.4887   $152.49   $152.50   $152.50  
  Purchase #7 $59.93   5.286%   $63.0979   $63.10   $63.10   $63.10  
  7 purchase totals = $993.54       $1,067.0106   $1,067.02   $1,067.05   $1,067.10