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	$241.52	7.852%	$260.4842	$260.48	$260.50	$260.50
Purchase #2	$96.48	9.643%	$105.7836	$105.78	$105.80	$105.80
Purchase #3	$226.27	13.720%	$257.3142	$257.31	$257.30	$257.30
Purchase #4	$13.89	11.549%	$15.4942	$15.49	$15.50	$15.50
Purchase #5	$77.54	6.160%	$82.3165	$82.32	$82.30	$82.30
Purchase #6	$59.66	3.509%	$61.7535	$61.75	$61.75	$61.80
Purchase #7	$190.99	11.240%	$212.4573	$212.46	$212.45	$212.50
7 purchase totals =	$906.35		$995.6035	$995.59	$995.60	$995.70