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	$56.89	5.195%	$59.8454	$59.85	$59.85	$59.80
Purchase #2	$240.66	8.198%	$260.3893	$260.39	$260.40	$260.40
Purchase #3	$233.47	8.342%	$252.9461	$252.95	$252.95	$252.90
Purchase #4	$101.82	3.559%	$105.4438	$105.44	$105.45	$105.40
Purchase #5	$132.59	12.267%	$148.8548	$148.85	$148.85	$148.90
Purchase #6	$242.88	5.839%	$257.0618	$257.06	$257.05	$257.10
Purchase #7	$103.70	5.635%	$109.5435	$109.54	$109.55	$109.50
7 purchase totals =	$1,112.01		$1,194.0847	$1,194.08	$1,194.10	$1,194.00