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	$101.58	9.734%	$111.4678	$111.47	$111.45	$111.50
Purchase #2	$185.76	11.553%	$207.2209	$207.22	$207.20	$207.20
Purchase #3	$128.62	10.722%	$142.4106	$142.41	$142.40	$142.40
Purchase #4	$44.35	10.251%	$48.8963	$48.90	$48.90	$48.90
Purchase #5	$6.88	13.402%	$7.8021	$7.80	$7.80	$7.80
Purchase #6	$92.76	13.451%	$105.2371	$105.24	$105.25	$105.20
Purchase #7	$119.52	11.845%	$133.6771	$133.68	$133.70	$133.70
7 purchase totals =	$679.47		$756.7119	$756.72	$756.70	$756.70