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	$212.49	13.853%	$241.9262	$241.93	$241.95	$241.90
Purchase #2	$221.37	13.867%	$252.0674	$252.07	$252.05	$252.10
Purchase #3	$11.53	7.707%	$12.4186	$12.42	$12.40	$12.40
Purchase #4	$97.87	11.686%	$109.3071	$109.31	$109.30	$109.30
Purchase #5	$55.80	10.368%	$61.5853	$61.59	$61.60	$61.60
Purchase #6	$158.73	12.611%	$178.7474	$178.75	$178.75	$178.70
Purchase #7	$112.59	13.154%	$127.4001	$127.40	$127.40	$127.40
7 purchase totals =	$870.38		$983.4521	$983.47	$983.45	$983.40