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	$61.78	5.475%	$65.1625	$65.16	$65.15	$65.20
Purchase #2	$248.97	7.127%	$266.7141	$266.71	$266.70	$266.70
Purchase #3	$96.27	9.690%	$105.5986	$105.60	$105.60	$105.60
Purchase #4	$14.48	4.719%	$15.1633	$15.16	$15.15	$15.20
Purchase #5	$212.76	8.456%	$230.751	$230.75	$230.75	$230.80
Purchase #6	$100.48	10.855%	$111.3871	$111.39	$111.40	$111.40
Purchase #7	$27.73	10.436%	$30.6239	$30.62	$30.60	$30.60
7 purchase totals =	$762.47		$825.4005	$825.39	$825.35	$825.50