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	$142.66	10.853%	$158.1429	$158.14	$158.15	$158.10
Purchase #2	$100.34	12.591%	$112.9738	$112.97	$112.95	$113.00
Purchase #3	$126.62	3.164%	$130.6263	$130.63	$130.65	$130.60
Purchase #4	$220.50	5.848%	$233.3948	$233.39	$233.40	$233.40
Purchase #5	$60.92	9.665%	$66.8079	$66.81	$66.80	$66.80
Purchase #6	$37.83	12.149%	$42.426	$42.43	$42.45	$42.40
Purchase #7	$38.98	11.337%	$43.3992	$43.40	$43.40	$43.40
7 purchase totals =	$727.85		$787.7709	$787.77	$787.80	$787.70