Robert Marian commented on Order Printer Sum of Taxes at certain Tax rate

Okay, thanks to the answer in this post I figured it out.

Here is how it looks like:

        {% assign tax9 = 0 %}
        {% for line_item in line_items %}
        {% for tax_line in line_item.tax_lines %}
        {% if tax_line.rate == 0.09 %}
        {% capture taxline9 %}
            {{ tax_line.price | times: line_item.quantity }}
        {% endcapture %}
        {% assign tax9 = tax9 | plus: taxline9  %}
        {% endif %}
        {% endfor %}
        {% endfor %}
        {{ tax9 | money }}