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	$217.67	6.118%	$230.9871	$230.99	$231.00	$231.00
Purchase #2	$234.77	8.667%	$255.1175	$255.12	$255.10	$255.10
Purchase #3	$204.68	4.600%	$214.0953	$214.10	$214.10	$214.10
Purchase #4	$215.54	11.863%	$241.1095	$241.11	$241.10	$241.10
Purchase #5	$48.47	9.478%	$53.064	$53.06	$53.05	$53.10
Purchase #6	$112.85	12.636%	$127.1097	$127.11	$127.10	$127.10
Purchase #7	$18.61	9.496%	$20.3772	$20.38	$20.40	$20.40
7 purchase totals =	$1,052.59		$1,141.8603	$1,141.87	$1,141.85	$1,141.90