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	$191.28	4.152%	$199.2219	$199.22	$199.20	$199.20
Purchase #2	$73.50	12.601%	$82.7617	$82.76	$82.75	$82.80
Purchase #3	$56.88	9.667%	$62.3786	$62.38	$62.40	$62.40
Purchase #4	$48.50	11.171%	$53.9179	$53.92	$53.90	$53.90
Purchase #5	$233.97	8.133%	$252.9988	$253.00	$253.00	$253.00
Purchase #6	$145.97	3.739%	$151.4278	$151.43	$151.45	$151.40
Purchase #7	$138.42	13.371%	$156.9281	$156.93	$156.95	$156.90
7 purchase totals =	$888.52		$959.6348	$959.64	$959.65	$959.60