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	$151.82	4.176%	$158.16	$158.16	$158.15	$158.20
Purchase #2	$59.90	11.153%	$66.5806	$66.58	$66.60	$66.60
Purchase #3	$147.45	11.670%	$164.6574	$164.66	$164.65	$164.70
Purchase #4	$70.90	9.386%	$77.5547	$77.55	$77.55	$77.60
Purchase #5	$49.83	8.492%	$54.0616	$54.06	$54.05	$54.10
Purchase #6	$207.50	8.251%	$224.6208	$224.62	$224.60	$224.60
Purchase #7	$114.99	11.741%	$128.491	$128.49	$128.50	$128.50
7 purchase totals =	$802.39		$874.1261	$874.12	$874.10	$874.30