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 $214.67   6.210%   $228.001   $228.00   $228.00   $228.00  
  Purchase #2 $71.99   6.549%   $76.7046   $76.70   $76.70   $76.70  
  Purchase #3 $58.77   7.519%   $63.1889   $63.19   $63.20   $63.20  
  Purchase #4 $67.85   13.295%   $76.8707   $76.87   $76.85   $76.90  
  Purchase #5 $136.56   5.160%   $143.6065   $143.61   $143.60   $143.60  
  Purchase #6 $210.30   3.645%   $217.9654   $217.97   $217.95   $218.00  
  Purchase #7 $146.92   8.556%   $159.4905   $159.49   $159.50   $159.50  
  7 purchase totals = $907.06       $965.8276   $965.83   $965.80   $965.90