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	$212.67	13.683%	$241.7696	$241.77	$241.75	$241.80
Purchase #2	$238.48	4.246%	$248.6059	$248.61	$248.60	$248.60
Purchase #3	$71.72	3.250%	$74.0509	$74.05	$74.05	$74.10
Purchase #4	$52.40	3.379%	$54.1706	$54.17	$54.15	$54.20
Purchase #5	$243.52	6.582%	$259.5485	$259.55	$259.55	$259.50
Purchase #6	$45.69	7.244%	$48.9998	$49.00	$49.00	$49.00
Purchase #7	$122.50	9.766%	$134.4634	$134.46	$134.45	$134.50
7 purchase totals =	$986.98		$1,061.6087	$1,061.61	$1,061.55	$1,061.70