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	$100.25	10.307%	$110.5828	$110.58	$110.60	$110.60
Purchase #2	$48.60	10.702%	$53.8012	$53.80	$53.80	$53.80
Purchase #3	$45.94	5.343%	$48.3946	$48.39	$48.40	$48.40
Purchase #4	$45.47	7.634%	$48.9412	$48.94	$48.95	$48.90
Purchase #5	$49.32	13.230%	$55.845	$55.85	$55.85	$55.80
Purchase #6	$37.62	8.138%	$40.6815	$40.68	$40.70	$40.70
Purchase #7	$107.60	6.493%	$114.5865	$114.59	$114.60	$114.60
7 purchase totals =	$434.80		$472.8328	$472.83	$472.90	$472.80