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	$99.50	12.229%	$111.6679	$111.67	$111.65	$111.70
Purchase #2	$173.36	10.327%	$191.2629	$191.26	$191.25	$191.30
Purchase #3	$18.53	10.301%	$20.4388	$20.44	$20.45	$20.40
Purchase #4	$68.99	4.202%	$71.889	$71.89	$71.90	$71.90
Purchase #5	$115.81	13.865%	$131.8671	$131.87	$131.85	$131.90
Purchase #6	$56.46	3.353%	$58.3531	$58.35	$58.35	$58.40
Purchase #7	$34.36	12.105%	$38.5193	$38.52	$38.50	$38.50
7 purchase totals =	$567.01		$623.9981	$624.00	$623.95	$624.10