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	$178.61	3.324%	$184.547	$184.55	$184.55	$184.50
Purchase #2	$96.41	7.624%	$103.7603	$103.76	$103.75	$103.80
Purchase #3	$159.81	4.200%	$166.522	$166.52	$166.50	$166.50
Purchase #4	$62.62	4.254%	$65.2839	$65.28	$65.30	$65.30
Purchase #5	$127.64	12.380%	$143.4418	$143.44	$143.45	$143.40
Purchase #6	$146.68	5.734%	$155.0906	$155.09	$155.10	$155.10
Purchase #7	$95.40	5.341%	$100.4953	$100.50	$100.50	$100.50
7 purchase totals =	$867.17		$919.1409	$919.14	$919.15	$919.10