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 $106.99   5.529%   $112.9055   $112.91   $112.90   $112.90  
  Purchase #2 $9.36   8.554%   $10.1607   $10.16   $10.15   $10.20  
  Purchase #3 $196.66   3.593%   $203.726   $203.73   $203.75   $203.70  
  Purchase #4 $77.68   5.710%   $82.1155   $82.12   $82.10   $82.10  
  Purchase #5 $232.79   8.480%   $252.5306   $252.53   $252.55   $252.50  
  Purchase #6 $206.93   3.678%   $214.5409   $214.54   $214.55   $214.50  
  Purchase #7 $142.59   10.249%   $157.204   $157.20   $157.20   $157.20  
  7 purchase totals = $973.00       $1,033.1832   $1,033.19   $1,033.20   $1,033.10