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	$105.83	5.453%	$111.6009	$111.60	$111.60	$111.60
Purchase #2	$19.63	9.643%	$21.5229	$21.52	$21.50	$21.50
Purchase #3	$101.57	11.873%	$113.6294	$113.63	$113.65	$113.60
Purchase #4	$177.98	6.340%	$189.2639	$189.26	$189.25	$189.30
Purchase #5	$114.80	11.340%	$127.8183	$127.82	$127.80	$127.80
Purchase #6	$16.97	4.597%	$17.7501	$17.75	$17.75	$17.80
Purchase #7	$117.25	8.806%	$127.575	$127.58	$127.60	$127.60
7 purchase totals =	$654.03		$709.1605	$709.16	$709.15	$709.20