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	$48.84	9.735%	$53.5946	$53.59	$53.60	$53.60
Purchase #2	$167.65	9.661%	$183.8467	$183.85	$183.85	$183.80
Purchase #3	$57.95	8.127%	$62.6596	$62.66	$62.65	$62.70
Purchase #4	$52.59	13.186%	$59.5245	$59.52	$59.50	$59.50
Purchase #5	$26.73	9.710%	$29.3255	$29.33	$29.35	$29.30
Purchase #6	$224.99	9.581%	$246.5463	$246.55	$246.55	$246.50
Purchase #7	$13.75	9.846%	$15.1038	$15.10	$15.10	$15.10
7 purchase totals =	$592.50		$650.6010	$650.60	$650.60	$650.50