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	$65.55	13.827%	$74.6136	$74.61	$74.60	$74.60
Purchase #2	$196.58	9.660%	$215.5696	$215.57	$215.55	$215.60
Purchase #3	$73.84	3.130%	$76.1512	$76.15	$76.15	$76.20
Purchase #4	$58.32	11.408%	$64.9731	$64.97	$64.95	$65.00
Purchase #5	$106.81	4.459%	$111.5727	$111.57	$111.55	$111.60
Purchase #6	$53.54	5.632%	$56.5554	$56.56	$56.55	$56.60
Purchase #7	$47.60	8.129%	$51.4694	$51.47	$51.45	$51.50
7 purchase totals =	$602.24		$650.9050	$650.90	$650.80	$651.10