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	$146.27	4.827%	$153.3305	$153.33	$153.35	$153.30
Purchase #2	$6.89	5.117%	$7.2426	$7.24	$7.25	$7.20
Purchase #3	$108.25	8.714%	$117.6829	$117.68	$117.70	$117.70
Purchase #4	$28.86	11.655%	$32.2236	$32.22	$32.20	$32.20
Purchase #5	$159.44	4.181%	$166.1062	$166.11	$166.10	$166.10
Purchase #6	$34.76	10.570%	$38.4341	$38.43	$38.45	$38.40
Purchase #7	$221.42	5.491%	$233.5782	$233.58	$233.60	$233.60
7 purchase totals =	$705.89		$748.5981	$748.59	$748.65	$748.50