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	$190.49	13.229%	$215.6899	$215.69	$215.70	$215.70
Purchase #2	$111.73	10.780%	$123.7745	$123.77	$123.75	$123.80
Purchase #3	$116.86	3.106%	$120.4897	$120.49	$120.50	$120.50
Purchase #4	$111.86	6.212%	$118.8087	$118.81	$118.80	$118.80
Purchase #5	$102.64	5.598%	$108.3858	$108.39	$108.40	$108.40
Purchase #6	$226.58	9.346%	$247.7562	$247.76	$247.75	$247.80
Purchase #7	$107.85	8.121%	$116.6085	$116.61	$116.60	$116.60
7 purchase totals =	$968.01		$1,051.5133	$1,051.52	$1,051.50	$1,051.60