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	$94.28	10.307%	$103.9974	$104.00	$104.00	$104.00
Purchase #2	$235.41	6.692%	$251.1636	$251.16	$251.15	$251.20
Purchase #3	$211.88	5.229%	$222.9592	$222.96	$222.95	$223.00
Purchase #4	$155.40	6.730%	$165.8584	$165.86	$165.85	$165.90
Purchase #5	$63.95	4.218%	$66.6474	$66.65	$66.65	$66.60
Purchase #6	$7.64	3.693%	$7.9221	$7.92	$7.90	$7.90
Purchase #7	$24.52	13.644%	$27.8655	$27.87	$27.85	$27.90
7 purchase totals =	$793.08		$846.4136	$846.42	$846.35	$846.50