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	$106.96	11.111%	$118.8443	$118.84	$118.85	$118.80
Purchase #2	$74.36	5.757%	$78.6409	$78.64	$78.65	$78.60
Purchase #3	$207.33	13.634%	$235.5974	$235.60	$235.60	$235.60
Purchase #4	$103.27	11.250%	$114.8879	$114.89	$114.90	$114.90
Purchase #5	$131.63	9.583%	$144.2441	$144.24	$144.25	$144.20
Purchase #6	$105.67	5.516%	$111.4988	$111.50	$111.50	$111.50
Purchase #7	$114.63	13.327%	$129.9067	$129.91	$129.90	$129.90
7 purchase totals =	$843.85		$933.6201	$933.62	$933.65	$933.50