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 $231.58   13.335%   $262.4612   $262.46   $262.45   $262.50  
  Purchase #2 $103.99   10.275%   $114.675   $114.68   $114.70   $114.70  
  Purchase #3 $67.63   4.637%   $70.766   $70.77   $70.75   $70.80  
  Purchase #4 $70.45   8.264%   $76.272   $76.27   $76.25   $76.30  
  Purchase #5 $215.31   3.268%   $222.3463   $222.35   $222.35   $222.30  
  Purchase #6 $246.82   9.659%   $270.6603   $270.66   $270.65   $270.70  
  Purchase #7 $38.78   9.430%   $42.437   $42.44   $42.45   $42.40  
  7 purchase totals = $974.56       $1,059.6178   $1,059.63   $1,059.60   $1,059.70