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	$106.62	4.501%	$111.419	$111.42	$111.40	$111.40
Purchase #2	$36.60	5.202%	$38.5039	$38.50	$38.50	$38.50
Purchase #3	$244.32	4.813%	$256.0791	$256.08	$256.10	$256.10
Purchase #4	$99.95	3.209%	$103.1574	$103.16	$103.15	$103.20
Purchase #5	$10.42	7.758%	$11.2284	$11.23	$11.25	$11.20
Purchase #6	$108.84	5.812%	$115.1658	$115.17	$115.15	$115.20
Purchase #7	$17.50	6.395%	$18.6191	$18.62	$18.60	$18.60
7 purchase totals =	$624.25		$654.1727	$654.18	$654.15	$654.20