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	$154.97	10.202%	$170.78	$170.78	$170.80	$170.80
Purchase #2	$63.94	12.126%	$71.6934	$71.69	$71.70	$71.70
Purchase #3	$148.86	13.174%	$168.4708	$168.47	$168.45	$168.50
Purchase #4	$49.33	11.267%	$54.888	$54.89	$54.90	$54.90
Purchase #5	$164.62	12.574%	$185.3193	$185.32	$185.30	$185.30
Purchase #6	$160.45	6.274%	$170.5166	$170.52	$170.50	$170.50
Purchase #7	$217.68	13.804%	$247.7285	$247.73	$247.75	$247.70
7 purchase totals =	$959.85		$1,069.3966	$1,069.40	$1,069.40	$1,069.40