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	$11.47	9.725%	$12.5855	$12.59	$12.60	$12.60
Purchase #2	$250.51	13.521%	$284.3815	$284.38	$284.40	$284.40
Purchase #3	$73.92	3.242%	$76.3165	$76.32	$76.30	$76.30
Purchase #4	$137.45	8.742%	$149.4659	$149.47	$149.45	$149.50
Purchase #5	$185.67	10.845%	$205.8059	$205.81	$205.80	$205.80
Purchase #6	$193.72	7.735%	$208.7042	$208.70	$208.70	$208.70
Purchase #7	$111.85	10.539%	$123.6379	$123.64	$123.65	$123.60
7 purchase totals =	$964.59		$1,060.8974	$1,060.91	$1,060.90	$1,060.90