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	$170.32	9.176%	$185.9486	$185.95	$185.95	$185.90
Purchase #2	$35.69	5.688%	$37.72	$37.72	$37.70	$37.70
Purchase #3	$51.27	10.819%	$56.8169	$56.82	$56.80	$56.80
Purchase #4	$86.58	9.762%	$95.0319	$95.03	$95.05	$95.00
Purchase #5	$33.88	10.388%	$37.3995	$37.40	$37.40	$37.40
Purchase #6	$42.83	12.204%	$48.057	$48.06	$48.05	$48.10
Purchase #7	$134.95	13.777%	$153.5421	$153.54	$153.55	$153.50
7 purchase totals =	$555.52		$614.5160	$614.52	$614.50	$614.40