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	$192.37	4.124%	$200.3033	$200.30	$200.30	$200.30
Purchase #2	$112.55	13.297%	$127.5158	$127.52	$127.50	$127.50
Purchase #3	$52.80	8.452%	$57.2627	$57.26	$57.25	$57.30
Purchase #4	$112.66	9.730%	$123.6218	$123.62	$123.60	$123.60
Purchase #5	$60.83	9.233%	$66.4464	$66.45	$66.45	$66.40
Purchase #6	$41.97	11.432%	$46.768	$46.77	$46.75	$46.80
Purchase #7	$199.27	6.798%	$212.8164	$212.82	$212.80	$212.80
7 purchase totals =	$772.45		$834.7344	$834.74	$834.65	$834.70