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	$133.59	9.723%	$146.579	$146.58	$146.60	$146.60
Purchase #2	$56.58	5.640%	$59.7711	$59.77	$59.75	$59.80
Purchase #3	$208.27	9.147%	$227.3205	$227.32	$227.30	$227.30
Purchase #4	$212.66	3.182%	$219.4268	$219.43	$219.45	$219.40
Purchase #5	$50.95	4.146%	$53.0624	$53.06	$53.05	$53.10
Purchase #6	$92.92	12.449%	$104.4876	$104.49	$104.50	$104.50
Purchase #7	$17.64	8.114%	$19.0713	$19.07	$19.05	$19.10
7 purchase totals =	$772.61		$829.7187	$829.72	$829.70	$829.80