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	$199.45	4.723%	$208.87	$208.87	$208.85	$208.90
Purchase #2	$135.76	9.610%	$148.8065	$148.81	$148.80	$148.80
Purchase #3	$12.64	10.196%	$13.9288	$13.93	$13.95	$13.90
Purchase #4	$152.89	7.654%	$164.5922	$164.59	$164.60	$164.60
Purchase #5	$27.80	10.515%	$30.7232	$30.72	$30.70	$30.70
Purchase #6	$134.38	5.853%	$142.2453	$142.25	$142.25	$142.20
Purchase #7	$217.39	3.211%	$224.3704	$224.37	$224.35	$224.40
7 purchase totals =	$880.31		$933.5364	$933.54	$933.50	$933.50