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	$214.76	5.506%	$226.5847	$226.58	$226.60	$226.60
Purchase #2	$90.42	4.108%	$94.1345	$94.13	$94.15	$94.10
Purchase #3	$29.71	5.528%	$31.3524	$31.35	$31.35	$31.40
Purchase #4	$104.52	13.292%	$118.4128	$118.41	$118.40	$118.40
Purchase #5	$26.91	5.115%	$28.2864	$28.29	$28.30	$28.30
Purchase #6	$172.32	7.123%	$184.5944	$184.59	$184.60	$184.60
Purchase #7	$49.51	5.333%	$52.1504	$52.15	$52.15	$52.20
7 purchase totals =	$688.15		$735.5156	$735.50	$735.55	$735.60