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	$230.75	9.806%	$253.3773	$253.38	$253.40	$253.40
Purchase #2	$60.71	4.506%	$63.4456	$63.45	$63.45	$63.40
Purchase #3	$242.39	10.131%	$266.9465	$266.95	$266.95	$266.90
Purchase #4	$71.27	6.625%	$75.9916	$75.99	$76.00	$76.00
Purchase #5	$107.83	3.317%	$111.4067	$111.41	$111.40	$111.40
Purchase #6	$245.78	13.569%	$279.1299	$279.13	$279.15	$279.10
Purchase #7	$59.63	12.813%	$67.2704	$67.27	$67.25	$67.30
7 purchase totals =	$1,018.36		$1,117.5680	$1,117.58	$1,117.60	$1,117.50