Do you use the checkbox-group? You can then use the setValue action of it to set the group. For checking/unchecking a single checkbox use the select action on the checkbox.
Uncheck checkbox group:
dmx-on:click="company_size.setValue([])"
Uncheck single checkbox:
dmx-on:click="checkbox1.select(false)"
Uncheck checkboxes with jQuery:
onclick="$('[name=company_size]').prop('checked', false)"