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	$160.38	7.677%	$172.6924	$172.69	$172.70	$172.70
Purchase #2	$118.73	13.335%	$134.5626	$134.56	$134.55	$134.60
Purchase #3	$99.53	7.717%	$107.2107	$107.21	$107.20	$107.20
Purchase #4	$12.78	8.551%	$13.8728	$13.87	$13.85	$13.90
Purchase #5	$141.47	12.325%	$158.9062	$158.91	$158.90	$158.90
Purchase #6	$141.43	10.658%	$156.5036	$156.50	$156.50	$156.50
Purchase #7	$111.52	4.786%	$116.8573	$116.86	$116.85	$116.90
7 purchase totals =	$785.84		$860.6056	$860.60	$860.55	$860.70