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	$190.44	4.827%	$199.6325	$199.63	$199.65	$199.60
Purchase #2	$48.95	10.235%	$53.96	$53.96	$53.95	$54.00
Purchase #3	$132.99	8.604%	$144.4325	$144.43	$144.45	$144.40
Purchase #4	$53.83	5.333%	$56.7008	$56.70	$56.70	$56.70
Purchase #5	$67.75	4.630%	$70.8868	$70.89	$70.90	$70.90
Purchase #6	$228.83	11.798%	$255.8274	$255.83	$255.85	$255.80
Purchase #7	$34.26	11.179%	$38.0899	$38.09	$38.10	$38.10
7 purchase totals =	$757.05		$819.5299	$819.53	$819.60	$819.50