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	$36.51	11.426%	$40.6816	$40.68	$40.70	$40.70
Purchase #2	$26.32	4.509%	$27.5068	$27.51	$27.50	$27.50
Purchase #3	$58.51	6.472%	$62.2968	$62.30	$62.30	$62.30
Purchase #4	$242.96	4.615%	$254.1726	$254.17	$254.15	$254.20
Purchase #5	$78.67	9.464%	$86.1153	$86.12	$86.10	$86.10
Purchase #6	$34.61	12.627%	$38.9802	$38.98	$39.00	$39.00
Purchase #7	$151.96	13.579%	$172.5946	$172.59	$172.60	$172.60
7 purchase totals =	$629.54		$682.3479	$682.35	$682.35	$682.40