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	$120.39	5.816%	$127.3919	$127.39	$127.40	$127.40
Purchase #2	$100.84	7.591%	$108.4948	$108.49	$108.50	$108.50
Purchase #3	$234.35	8.240%	$253.6604	$253.66	$253.65	$253.70
Purchase #4	$7.71	7.623%	$8.2977	$8.30	$8.30	$8.30
Purchase #5	$246.32	13.422%	$279.3811	$279.38	$279.40	$279.40
Purchase #6	$157.27	11.608%	$175.5259	$175.53	$175.55	$175.50
Purchase #7	$97.35	3.418%	$100.6774	$100.68	$100.70	$100.70
7 purchase totals =	$964.23		$1,053.4292	$1,053.43	$1,053.50	$1,053.50