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	$221.74	7.456%	$238.2729	$238.27	$238.25	$238.30
Purchase #2	$241.48	5.662%	$255.1526	$255.15	$255.15	$255.20
Purchase #3	$205.54	12.809%	$231.8676	$231.87	$231.85	$231.90
Purchase #4	$158.51	12.744%	$178.7105	$178.71	$178.70	$178.70
Purchase #5	$60.54	8.116%	$65.4534	$65.45	$65.45	$65.50
Purchase #6	$122.68	3.829%	$127.3774	$127.38	$127.40	$127.40
Purchase #7	$26.78	11.439%	$29.8434	$29.84	$29.85	$29.80
7 purchase totals =	$1,037.27		$1,126.6778	$1,126.67	$1,126.65	$1,126.80