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	$178.64	8.733%	$194.2406	$194.24	$194.25	$194.20
Purchase #2	$183.47	7.235%	$196.7441	$196.74	$196.75	$196.70
Purchase #3	$170.86	7.866%	$184.2998	$184.30	$184.30	$184.30
Purchase #4	$150.74	5.223%	$158.6132	$158.61	$158.60	$158.60
Purchase #5	$18.92	6.236%	$20.0999	$20.10	$20.10	$20.10
Purchase #6	$126.98	13.634%	$144.2925	$144.29	$144.30	$144.30
Purchase #7	$159.76	7.858%	$172.3139	$172.31	$172.30	$172.30
7 purchase totals =	$989.37		$1,070.6040	$1,070.59	$1,070.60	$1,070.50