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	$62.79	6.664%	$66.9743	$66.97	$66.95	$67.00
Purchase #2	$165.46	4.493%	$172.8941	$172.89	$172.90	$172.90
Purchase #3	$12.68	5.429%	$13.3684	$13.37	$13.35	$13.40
Purchase #4	$131.29	13.205%	$148.6268	$148.63	$148.65	$148.60
Purchase #5	$237.83	13.316%	$269.4994	$269.50	$269.50	$269.50
Purchase #6	$181.84	5.724%	$192.2485	$192.25	$192.25	$192.20
Purchase #7	$121.42	8.341%	$131.5476	$131.55	$131.55	$131.50
7 purchase totals =	$913.31		$995.1591	$995.16	$995.15	$995.10