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	$45.87	5.767%	$48.5153	$48.52	$48.50	$48.50
Purchase #2	$245.87	13.472%	$278.9936	$278.99	$279.00	$279.00
Purchase #3	$14.71	8.589%	$15.9734	$15.97	$15.95	$16.00
Purchase #4	$228.91	11.437%	$255.0904	$255.09	$255.10	$255.10
Purchase #5	$100.51	10.466%	$111.0294	$111.03	$111.05	$111.00
Purchase #6	$113.67	7.447%	$122.135	$122.14	$122.15	$122.10
Purchase #7	$164.61	10.236%	$181.4595	$181.46	$181.45	$181.50
7 purchase totals =	$914.15		$1,013.1966	$1,013.20	$1,013.20	$1,013.20