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	$208.43	4.427%	$217.6572	$217.66	$217.65	$217.70
Purchase #2	$140.91	9.632%	$154.4825	$154.48	$154.50	$154.50
Purchase #3	$146.41	5.823%	$154.9355	$154.94	$154.95	$154.90
Purchase #4	$49.88	7.184%	$53.4634	$53.46	$53.45	$53.50
Purchase #5	$87.57	3.274%	$90.437	$90.44	$90.45	$90.40
Purchase #6	$137.86	3.638%	$142.8753	$142.88	$142.90	$142.90
Purchase #7	$48.94	8.681%	$53.1885	$53.19	$53.20	$53.20
7 purchase totals =	$820.00		$867.0394	$867.05	$867.10	$867.10