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	$242.32	4.348%	$252.8561	$252.86	$252.85	$252.90
Purchase #2	$207.44	7.241%	$222.4607	$222.46	$222.45	$222.50
Purchase #3	$139.84	13.378%	$158.5478	$158.55	$158.55	$158.50
Purchase #4	$116.38	9.568%	$127.5152	$127.52	$127.50	$127.50
Purchase #5	$126.28	10.685%	$139.773	$139.77	$139.75	$139.80
Purchase #6	$49.95	9.550%	$54.7202	$54.72	$54.70	$54.70
Purchase #7	$69.53	11.557%	$77.5656	$77.57	$77.55	$77.60
7 purchase totals =	$951.74		$1,033.4386	$1,033.45	$1,033.35	$1,033.50