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	$78.25	5.550%	$82.5929	$82.59	$82.60	$82.60
Purchase #2	$108.61	13.138%	$122.8792	$122.88	$122.90	$122.90
Purchase #3	$34.61	9.819%	$38.0084	$38.01	$38.00	$38.00
Purchase #4	$32.80	8.123%	$35.4643	$35.46	$35.45	$35.50
Purchase #5	$78.90	13.665%	$89.6817	$89.68	$89.70	$89.70
Purchase #6	$214.65	7.188%	$230.079	$230.08	$230.10	$230.10
Purchase #7	$115.50	13.128%	$130.6628	$130.66	$130.65	$130.70
7 purchase totals =	$663.32		$729.3683	$729.36	$729.40	$729.50