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	$47.96	13.865%	$54.6097	$54.61	$54.60	$54.60
Purchase #2	$242.80	6.174%	$257.7905	$257.79	$257.80	$257.80
Purchase #3	$184.94	8.501%	$200.6617	$200.66	$200.65	$200.70
Purchase #4	$45.26	13.271%	$51.2665	$51.27	$51.25	$51.30
Purchase #5	$113.67	8.227%	$123.0216	$123.02	$123.00	$123.00
Purchase #6	$107.45	5.602%	$113.4693	$113.47	$113.45	$113.50
Purchase #7	$204.58	5.230%	$215.2795	$215.28	$215.30	$215.30
7 purchase totals =	$946.66		$1,016.0988	$1,016.10	$1,016.05	$1,016.20