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	$74.90	9.490%	$82.008	$82.01	$82.00	$82.00
Purchase #2	$56.25	9.674%	$61.6916	$61.69	$61.70	$61.70
Purchase #3	$51.85	5.623%	$54.7655	$54.77	$54.75	$54.80
Purchase #4	$149.98	5.773%	$158.6383	$158.64	$158.65	$158.60
Purchase #5	$124.50	9.847%	$136.7595	$136.76	$136.75	$136.80
Purchase #6	$104.52	6.670%	$111.4915	$111.49	$111.50	$111.50
Purchase #7	$178.57	11.772%	$199.5913	$199.59	$199.60	$199.60
7 purchase totals =	$740.57		$804.9457	$804.95	$804.95	$805.00