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	$52.88	13.104%	$59.8094	$59.81	$59.80	$59.80
Purchase #2	$139.66	10.266%	$153.9975	$154.00	$154.00	$154.00
Purchase #3	$48.42	11.262%	$53.8731	$53.87	$53.85	$53.90
Purchase #4	$87.47	3.452%	$90.4895	$90.49	$90.50	$90.50
Purchase #5	$100.75	10.350%	$111.1776	$111.18	$111.20	$111.20
Purchase #6	$43.94	6.623%	$46.8501	$46.85	$46.85	$46.90
Purchase #7	$161.70	7.636%	$174.0474	$174.05	$174.05	$174.00
7 purchase totals =	$634.82		$690.2446	$690.25	$690.25	$690.30