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	$144.68	9.509%	$158.4376	$158.44	$158.45	$158.40
Purchase #2	$250.78	8.329%	$271.6675	$271.67	$271.65	$271.70
Purchase #3	$71.89	8.754%	$78.1833	$78.18	$78.20	$78.20
Purchase #4	$50.44	4.267%	$52.5923	$52.59	$52.60	$52.60
Purchase #5	$97.25	11.846%	$108.7702	$108.77	$108.75	$108.80
Purchase #6	$121.51	10.505%	$134.2746	$134.27	$134.25	$134.30
Purchase #7	$40.92	4.222%	$42.6476	$42.65	$42.65	$42.60
7 purchase totals =	$777.47		$846.5731	$846.57	$846.55	$846.60