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	$54.52	9.717%	$59.8177	$59.82	$59.80	$59.80
Purchase #2	$95.87	10.551%	$105.9852	$105.99	$106.00	$106.00
Purchase #3	$155.83	3.273%	$160.9303	$160.93	$160.95	$160.90
Purchase #4	$140.91	7.590%	$151.6051	$151.61	$151.60	$151.60
Purchase #5	$45.28	3.379%	$46.81	$46.81	$46.80	$46.80
Purchase #6	$17.77	10.201%	$19.5827	$19.58	$19.60	$19.60
Purchase #7	$134.83	12.669%	$151.9116	$151.91	$151.90	$151.90
7 purchase totals =	$645.01		$696.6426	$696.65	$696.65	$696.60