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	$86.37	10.514%	$95.4509	$95.45	$95.45	$95.50
Purchase #2	$215.57	10.693%	$238.6209	$238.62	$238.60	$238.60
Purchase #3	$232.42	7.315%	$249.4215	$249.42	$249.40	$249.40
Purchase #4	$9.81	13.338%	$11.1185	$11.12	$11.10	$11.10
Purchase #5	$51.77	6.649%	$55.2122	$55.21	$55.20	$55.20
Purchase #6	$131.94	4.534%	$137.9222	$137.92	$137.90	$137.90
Purchase #7	$52.37	13.205%	$59.2855	$59.29	$59.30	$59.30
7 purchase totals =	$780.25		$847.0317	$847.03	$846.95	$847.00