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	$145.77	8.126%	$157.6153	$157.62	$157.60	$157.60
Purchase #2	$40.33	5.171%	$42.4155	$42.42	$42.40	$42.40
Purchase #3	$39.81	4.453%	$41.5827	$41.58	$41.60	$41.60
Purchase #4	$98.41	5.733%	$104.0518	$104.05	$104.05	$104.10
Purchase #5	$50.94	11.655%	$56.8771	$56.88	$56.90	$56.90
Purchase #6	$158.85	9.218%	$173.4928	$173.49	$173.50	$173.50
Purchase #7	$103.99	13.844%	$118.3864	$118.39	$118.40	$118.40
7 purchase totals =	$638.10		$694.4216	$694.43	$694.45	$694.50