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	$148.27	13.727%	$168.623	$168.62	$168.60	$168.60
Purchase #2	$248.26	7.447%	$266.7479	$266.75	$266.75	$266.70
Purchase #3	$232.81	9.858%	$255.7604	$255.76	$255.75	$255.80
Purchase #4	$105.93	10.187%	$116.7211	$116.72	$116.70	$116.70
Purchase #5	$27.49	13.215%	$31.1228	$31.12	$31.10	$31.10
Purchase #6	$153.76	5.749%	$162.5997	$162.60	$162.60	$162.60
Purchase #7	$45.77	12.162%	$51.3365	$51.34	$51.35	$51.30
7 purchase totals =	$962.29		$1,052.9114	$1,052.91	$1,052.85	$1,052.80