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	$9.46	6.309%	$10.0568	$10.06	$10.05	$10.10
Purchase #2	$39.31	11.546%	$43.8487	$43.85	$43.85	$43.80
Purchase #3	$74.97	3.536%	$77.6209	$77.62	$77.60	$77.60
Purchase #4	$38.83	3.357%	$40.1335	$40.13	$40.15	$40.10
Purchase #5	$230.60	5.123%	$242.4136	$242.41	$242.40	$242.40
Purchase #6	$21.81	3.153%	$22.4977	$22.50	$22.50	$22.50
Purchase #7	$167.48	13.448%	$190.0027	$190.00	$190.00	$190.00
7 purchase totals =	$582.46		$626.5739	$626.57	$626.55	$626.50