The inherent problem with getting the price is that the price displayed/generated on the info page is embedded in text, so you can't use that in-built function to just get the number.

Hence in jscript_plugin_structured_data, the price is manually calculated:

PHP Code:
        //get the price with tax 
$product_display_price_value = round(zen_get_products_actual_price($product_id) * (1 + zen_get_tax_rate($tax_class_id) / 100), 2);//show price with tax, decimal point (not comma), two decimal places 
So you need to fiddle with that to get the rounding you need.