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	$233.45	6.108%	$247.7091	$247.71	$247.70	$247.70
Purchase #2	$101.49	9.444%	$111.0747	$111.07	$111.05	$111.10
Purchase #3	$34.55	8.866%	$37.6132	$37.61	$37.60	$37.60
Purchase #4	$235.71	4.646%	$246.6611	$246.66	$246.65	$246.70
Purchase #5	$124.84	10.842%	$138.3752	$138.38	$138.40	$138.40
Purchase #6	$241.86	5.815%	$255.9242	$255.92	$255.90	$255.90
Purchase #7	$34.97	6.633%	$37.2896	$37.29	$37.30	$37.30
7 purchase totals =	$1,006.87		$1,074.6471	$1,074.64	$1,074.60	$1,074.70