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	$17.41	11.341%	$19.3845	$19.38	$19.40	$19.40
Purchase #2	$224.70	8.790%	$244.4511	$244.45	$244.45	$244.50
Purchase #3	$33.46	10.708%	$37.0429	$37.04	$37.05	$37.00
Purchase #4	$136.79	5.466%	$144.2669	$144.27	$144.25	$144.30
Purchase #5	$52.58	4.448%	$54.9188	$54.92	$54.90	$54.90
Purchase #6	$138.42	8.682%	$150.4376	$150.44	$150.45	$150.40
Purchase #7	$56.42	12.806%	$63.6451	$63.65	$63.65	$63.60
7 purchase totals =	$659.78		$714.1469	$714.15	$714.15	$714.10