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	$236.76	6.229%	$251.5078	$251.51	$251.50	$251.50
Purchase #2	$9.27	8.389%	$10.0477	$10.05	$10.05	$10.00
Purchase #3	$120.53	5.745%	$127.4544	$127.45	$127.45	$127.50
Purchase #4	$165.92	13.443%	$188.2246	$188.22	$188.20	$188.20
Purchase #5	$30.42	3.722%	$31.5522	$31.55	$31.55	$31.60
Purchase #6	$169.87	5.795%	$179.714	$179.71	$179.70	$179.70
Purchase #7	$143.67	5.573%	$151.6767	$151.68	$151.70	$151.70
7 purchase totals =	$876.44		$940.1774	$940.17	$940.15	$940.20