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	$149.70	5.832%	$158.4305	$158.43	$158.45	$158.40
Purchase #2	$98.38	5.439%	$103.7309	$103.73	$103.75	$103.70
Purchase #3	$132.85	11.600%	$148.2606	$148.26	$148.25	$148.30
Purchase #4	$88.63	10.108%	$97.5887	$97.59	$97.60	$97.60
Purchase #5	$29.98	8.187%	$32.4345	$32.43	$32.45	$32.40
Purchase #6	$56.98	4.766%	$59.6957	$59.70	$59.70	$59.70
Purchase #7	$12.91	13.532%	$14.657	$14.66	$14.65	$14.70
7 purchase totals =	$569.43		$614.7979	$614.80	$614.85	$614.80