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	$105.52	5.194%	$111.0007	$111.00	$111.00	$111.00
Purchase #2	$148.86	8.474%	$161.4744	$161.47	$161.45	$161.50
Purchase #3	$90.26	8.687%	$98.1009	$98.10	$98.10	$98.10
Purchase #4	$70.57	11.131%	$78.4251	$78.43	$78.45	$78.40
Purchase #5	$97.62	3.284%	$100.8258	$100.83	$100.85	$100.80
Purchase #6	$192.80	3.366%	$199.2896	$199.29	$199.30	$199.30
Purchase #7	$12.74	9.583%	$13.9609	$13.96	$13.95	$14.00
7 purchase totals =	$718.37		$763.0774	$763.08	$763.10	$763.10