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	$62.68	4.789%	$65.6817	$65.68	$65.70	$65.70
Purchase #2	$207.64	10.102%	$228.6158	$228.62	$228.60	$228.60
Purchase #3	$156.63	10.410%	$172.9352	$172.94	$172.95	$172.90
Purchase #4	$136.25	11.626%	$152.0904	$152.09	$152.10	$152.10
Purchase #5	$34.58	13.409%	$39.2168	$39.22	$39.20	$39.20
Purchase #6	$209.90	5.605%	$221.6649	$221.66	$221.65	$221.70
Purchase #7	$127.90	6.458%	$136.1598	$136.16	$136.15	$136.20
7 purchase totals =	$935.58		$1,016.3646	$1,016.37	$1,016.35	$1,016.40