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	$82.66	7.731%	$89.0504	$89.05	$89.05	$89.10
Purchase #2	$47.83	7.856%	$51.5875	$51.59	$51.60	$51.60
Purchase #3	$30.61	6.779%	$32.6851	$32.69	$32.70	$32.70
Purchase #4	$230.41	7.485%	$247.6562	$247.66	$247.65	$247.70
Purchase #5	$95.66	12.643%	$107.7543	$107.75	$107.75	$107.80
Purchase #6	$184.43	8.551%	$200.2006	$200.20	$200.20	$200.20
Purchase #7	$130.71	10.509%	$144.4463	$144.45	$144.45	$144.40
7 purchase totals =	$802.31		$873.3804	$873.39	$873.40	$873.50