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	$48.41	10.724%	$53.6015	$53.60	$53.60	$53.60
Purchase #2	$42.30	4.694%	$44.2856	$44.29	$44.30	$44.30
Purchase #3	$207.60	4.766%	$217.4942	$217.49	$217.50	$217.50
Purchase #4	$54.37	13.613%	$61.7714	$61.77	$61.75	$61.80
Purchase #5	$19.72	7.189%	$21.1377	$21.14	$21.15	$21.10
Purchase #6	$91.77	8.630%	$99.6898	$99.69	$99.70	$99.70
Purchase #7	$58.92	7.642%	$63.4227	$63.42	$63.40	$63.40
7 purchase totals =	$523.09		$561.4029	$561.40	$561.40	$561.40