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	$214.41	11.113%	$238.2374	$238.24	$238.25	$238.20
Purchase #2	$112.40	13.644%	$127.7359	$127.74	$127.75	$127.70
Purchase #3	$235.87	7.524%	$253.6169	$253.62	$253.60	$253.60
Purchase #4	$107.85	3.333%	$111.4446	$111.44	$111.45	$111.40
Purchase #5	$231.66	12.257%	$260.0546	$260.05	$260.05	$260.10
Purchase #6	$92.83	9.350%	$101.5096	$101.51	$101.50	$101.50
Purchase #7	$71.50	4.514%	$74.7275	$74.73	$74.75	$74.70
7 purchase totals =	$1,066.52		$1,167.3265	$1,167.33	$1,167.35	$1,167.20