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	$64.26	8.307%	$69.5981	$69.60	$69.60	$69.60
Purchase #2	$228.40	10.370%	$252.0851	$252.09	$252.10	$252.10
Purchase #3	$152.51	8.106%	$164.8725	$164.87	$164.85	$164.90
Purchase #4	$181.73	6.123%	$192.8573	$192.86	$192.85	$192.90
Purchase #5	$103.39	8.236%	$111.9052	$111.91	$111.90	$111.90
Purchase #6	$198.95	6.418%	$211.7186	$211.72	$211.70	$211.70
Purchase #7	$40.70	12.773%	$45.8986	$45.90	$45.90	$45.90
7 purchase totals =	$969.94		$1,048.9354	$1,048.95	$1,048.90	$1,049.00