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	$132.34	7.152%	$141.805	$141.81	$141.80	$141.80
Purchase #2	$138.43	12.872%	$156.2487	$156.25	$156.25	$156.20
Purchase #3	$158.92	10.388%	$175.4286	$175.43	$175.45	$175.40
Purchase #4	$34.68	12.388%	$38.9762	$38.98	$39.00	$39.00
Purchase #5	$59.60	11.318%	$66.3455	$66.35	$66.35	$66.30
Purchase #6	$156.46	5.363%	$164.8509	$164.85	$164.85	$164.90
Purchase #7	$29.50	5.546%	$31.1361	$31.14	$31.15	$31.10
7 purchase totals =	$709.93		$774.7910	$774.81	$774.85	$774.70