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	$9.72	11.723%	$10.8595	$10.86	$10.85	$10.90
Purchase #2	$224.83	6.483%	$239.4057	$239.41	$239.40	$239.40
Purchase #3	$48.87	11.822%	$54.6474	$54.65	$54.65	$54.60
Purchase #4	$54.96	11.701%	$61.3909	$61.39	$61.40	$61.40
Purchase #5	$78.75	6.491%	$83.8617	$83.86	$83.85	$83.90
Purchase #6	$208.42	6.105%	$221.144	$221.14	$221.15	$221.10
Purchase #7	$205.61	4.195%	$214.2353	$214.24	$214.25	$214.20
7 purchase totals =	$831.16		$885.5445	$885.55	$885.55	$885.50