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	$228.71	10.279%	$252.2191	$252.22	$252.20	$252.20
Purchase #2	$184.45	6.509%	$196.4559	$196.46	$196.45	$196.50
Purchase #3	$209.84	9.554%	$229.8881	$229.89	$229.90	$229.90
Purchase #4	$184.52	13.472%	$209.3785	$209.38	$209.40	$209.40
Purchase #5	$121.71	8.773%	$132.3876	$132.39	$132.40	$132.40
Purchase #6	$173.93	9.444%	$190.3559	$190.36	$190.35	$190.40
Purchase #7	$167.42	7.286%	$179.6182	$179.62	$179.60	$179.60
7 purchase totals =	$1,270.58		$1,390.3033	$1,390.32	$1,390.30	$1,390.40