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	$200.74	10.539%	$221.896	$221.90	$221.90	$221.90
Purchase #2	$68.64	5.843%	$72.6506	$72.65	$72.65	$72.70
Purchase #3	$183.81	4.176%	$191.4859	$191.49	$191.50	$191.50
Purchase #4	$102.44	8.569%	$111.2181	$111.22	$111.20	$111.20
Purchase #5	$65.50	7.773%	$70.5913	$70.59	$70.60	$70.60
Purchase #6	$107.41	10.767%	$118.9748	$118.97	$118.95	$119.00
Purchase #7	$57.46	3.447%	$59.4406	$59.44	$59.45	$59.40
7 purchase totals =	$786.00		$846.2573	$846.26	$846.25	$846.30