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	$41.81	6.721%	$44.6201	$44.62	$44.60	$44.60
Purchase #2	$66.78	7.782%	$71.9768	$71.98	$72.00	$72.00
Purchase #3	$220.73	4.324%	$230.2744	$230.27	$230.25	$230.30
Purchase #4	$122.47	3.548%	$126.8152	$126.82	$126.80	$126.80
Purchase #5	$48.42	4.342%	$50.5224	$50.52	$50.50	$50.50
Purchase #6	$49.43	11.382%	$55.0561	$55.06	$55.05	$55.10
Purchase #7	$175.65	11.696%	$196.194	$196.19	$196.20	$196.20
7 purchase totals =	$725.29		$775.4590	$775.46	$775.40	$775.50