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	$103.70	7.214%	$111.1809	$111.18	$111.20	$111.20
Purchase #2	$142.66	11.283%	$158.7563	$158.76	$158.75	$158.80
Purchase #3	$129.43	13.461%	$146.8526	$146.85	$146.85	$146.90
Purchase #4	$48.75	12.657%	$54.9203	$54.92	$54.90	$54.90
Purchase #5	$193.25	3.628%	$200.2611	$200.26	$200.25	$200.30
Purchase #6	$155.71	5.284%	$163.9377	$163.94	$163.95	$163.90
Purchase #7	$9.57	5.830%	$10.1279	$10.13	$10.15	$10.10
7 purchase totals =	$783.07		$846.0368	$846.04	$846.05	$846.10