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	$48.83	10.221%	$53.8209	$53.82	$53.80	$53.80
Purchase #2	$244.96	4.614%	$256.2625	$256.26	$256.25	$256.30
Purchase #3	$238.62	7.195%	$255.7887	$255.79	$255.80	$255.80
Purchase #4	$194.74	13.838%	$221.6881	$221.69	$221.70	$221.70
Purchase #5	$138.46	13.509%	$157.1646	$157.16	$157.15	$157.20
Purchase #6	$82.97	11.761%	$92.7281	$92.73	$92.75	$92.70
Purchase #7	$134.52	6.177%	$142.8293	$142.83	$142.85	$142.80
7 purchase totals =	$1,083.10		$1,180.2822	$1,180.28	$1,180.30	$1,180.30