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	$111.49	13.545%	$126.5913	$126.59	$126.60	$126.60
Purchase #2	$104.41	5.128%	$109.7641	$109.76	$109.75	$109.80
Purchase #3	$82.77	11.475%	$92.2679	$92.27	$92.25	$92.30
Purchase #4	$192.72	3.288%	$199.0566	$199.06	$199.05	$199.10
Purchase #5	$148.25	11.365%	$165.0986	$165.10	$165.10	$165.10
Purchase #6	$28.87	12.533%	$32.4883	$32.49	$32.50	$32.50
Purchase #7	$127.76	13.810%	$145.4037	$145.40	$145.40	$145.40
7 purchase totals =	$796.27		$870.6705	$870.67	$870.65	$870.80