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	$99.89	11.647%	$111.5242	$111.52	$111.50	$111.50
Purchase #2	$176.60	3.388%	$182.5832	$182.58	$182.60	$182.60
Purchase #3	$223.99	4.198%	$233.3931	$233.39	$233.40	$233.40
Purchase #4	$143.89	9.321%	$157.302	$157.30	$157.30	$157.30
Purchase #5	$49.52	3.724%	$51.3641	$51.36	$51.35	$51.40
Purchase #6	$195.49	11.145%	$217.2774	$217.28	$217.30	$217.30
Purchase #7	$110.86	6.673%	$118.2577	$118.26	$118.25	$118.30
7 purchase totals =	$1,000.24		$1,071.7017	$1,071.69	$1,071.70	$1,071.80