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	$106.52	4.441%	$111.2506	$111.25	$111.25	$111.30
Purchase #2	$32.91	6.163%	$34.9382	$34.94	$34.95	$34.90
Purchase #3	$59.45	4.634%	$62.2049	$62.20	$62.20	$62.20
Purchase #4	$51.58	9.433%	$56.4455	$56.45	$56.45	$56.40
Purchase #5	$155.44	5.497%	$163.9845	$163.98	$164.00	$164.00
Purchase #6	$105.95	3.347%	$109.4961	$109.50	$109.50	$109.50
Purchase #7	$176.87	13.442%	$200.6449	$200.64	$200.65	$200.60
7 purchase totals =	$688.72		$738.9647	$738.96	$739.00	$738.90