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	$158.69	8.776%	$172.6166	$172.62	$172.60	$172.60
Purchase #2	$240.52	9.665%	$263.7663	$263.77	$263.75	$263.80
Purchase #3	$159.93	5.753%	$169.1308	$169.13	$169.15	$169.10
Purchase #4	$211.27	6.677%	$225.3765	$225.38	$225.40	$225.40
Purchase #5	$53.46	3.396%	$55.2755	$55.28	$55.30	$55.30
Purchase #6	$101.36	9.762%	$111.2548	$111.25	$111.25	$111.30
Purchase #7	$26.51	4.312%	$27.6531	$27.65	$27.65	$27.70
7 purchase totals =	$951.74		$1,025.0736	$1,025.08	$1,025.10	$1,025.20