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	$15.34	4.191%	$15.9829	$15.98	$16.00	$16.00
Purchase #2	$47.55	13.606%	$54.0197	$54.02	$54.00	$54.00
Purchase #3	$157.81	6.455%	$167.9966	$168.00	$168.00	$168.00
Purchase #4	$127.46	13.619%	$144.8188	$144.82	$144.80	$144.80
Purchase #5	$56.46	11.486%	$62.945	$62.95	$62.95	$62.90
Purchase #6	$74.51	10.683%	$82.4699	$82.47	$82.45	$82.50
Purchase #7	$239.30	3.573%	$247.8502	$247.85	$247.85	$247.90
7 purchase totals =	$718.43		$776.0831	$776.09	$776.05	$776.10