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	$11.32	4.160%	$11.7909	$11.79	$11.80	$11.80
Purchase #2	$117.36	11.202%	$130.5067	$130.51	$130.50	$130.50
Purchase #3	$165.82	3.503%	$171.6287	$171.63	$171.65	$171.60
Purchase #4	$100.51	10.460%	$111.0233	$111.02	$111.00	$111.00
Purchase #5	$20.51	3.210%	$21.1684	$21.17	$21.15	$21.20
Purchase #6	$244.36	3.788%	$253.6164	$253.62	$253.60	$253.60
Purchase #7	$13.94	7.839%	$15.0328	$15.03	$15.05	$15.00
7 purchase totals =	$673.82		$714.7672	$714.77	$714.75	$714.70