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 $208.86   4.149%   $217.5256   $217.53   $217.55   $217.50  
  Purchase #2 $214.92   10.432%   $237.3405   $237.34   $237.35   $237.30  
  Purchase #3 $5.65   9.262%   $6.1733   $6.17   $6.15   $6.20  
  Purchase #4 $47.35   12.670%   $53.3492   $53.35   $53.35   $53.30  
  Purchase #5 $142.27   7.727%   $153.2632   $153.26   $153.25   $153.30  
  Purchase #6 $128.73   13.776%   $146.4638   $146.46   $146.45   $146.50  
  Purchase #7 $206.76   5.407%   $217.9395   $217.94   $217.95   $217.90  
  7 purchase totals = $954.54       $1,032.0551   $1,032.05   $1,032.05   $1,032.00