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	$63.76	10.496%	$70.4522	$70.45	$70.45	$70.50
Purchase #2	$87.55	13.565%	$99.4262	$99.43	$99.45	$99.40
Purchase #3	$190.76	7.293%	$204.6721	$204.67	$204.65	$204.70
Purchase #4	$29.60	9.366%	$32.3723	$32.37	$32.35	$32.40
Purchase #5	$178.29	4.396%	$186.1276	$186.13	$186.15	$186.10
Purchase #6	$100.29	11.644%	$111.9678	$111.97	$111.95	$112.00
Purchase #7	$12.51	6.343%	$13.3035	$13.30	$13.30	$13.30
7 purchase totals =	$662.76		$718.3217	$718.32	$718.30	$718.40