From ZF2's documentation at http://framework.zend.com/manual/2.3/en/modules/zend.i18n.view.helpers.html
I found the following link:
http://www.icu-project.org/apiref/icu4c/classDecimalFormat.html#details
If you scroll down to the decimal format and significant digits sections, you'll see the answer. I ended up doing this for my code to represent BTC:
$cur = getCurrency();
$this->plugin("currencyformat")->setCurrencyCode($cur);
if($cur == "BTC"):
$this->plugin("currencyformat")->setCurrencyPattern('@############### ¤');
endif;
The '@' means display at least one signification digit. The 15 '#'s plus the '@' means the maximum amount of significant digits to show is 16. The '¤' will display the currency at the end of the number.