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	$62.30	5.174%	$65.5234	$65.52	$65.50	$65.50
Purchase #2	$53.40	12.724%	$60.1946	$60.19	$60.20	$60.20
Purchase #3	$103.98	7.169%	$111.4343	$111.43	$111.45	$111.40
Purchase #4	$121.76	4.770%	$127.568	$127.57	$127.55	$127.60
Purchase #5	$177.59	12.782%	$200.2896	$200.29	$200.30	$200.30
Purchase #6	$166.49	12.644%	$187.541	$187.54	$187.55	$187.50
Purchase #7	$19.32	6.509%	$20.5775	$20.58	$20.60	$20.60
7 purchase totals =	$704.84		$773.1284	$773.12	$773.15	$773.10