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	$131.39	9.329%	$143.6474	$143.65	$143.65	$143.60
Purchase #2	$114.98	11.102%	$127.7451	$127.75	$127.75	$127.70
Purchase #3	$93.94	12.431%	$105.6177	$105.62	$105.60	$105.60
Purchase #4	$186.52	11.743%	$208.423	$208.42	$208.40	$208.40
Purchase #5	$57.35	4.250%	$59.7874	$59.79	$59.80	$59.80
Purchase #6	$208.43	6.686%	$222.3656	$222.37	$222.35	$222.40
Purchase #7	$70.68	7.853%	$76.2305	$76.23	$76.25	$76.20
7 purchase totals =	$863.29		$943.8167	$943.83	$943.80	$943.70