Can we set up tiered bulk discounts based on quantity added to cart for customers that aren't logged in?

Are volume discounts (Quantity Breaks) available for all customers even when they are not logged in?

Yes. Custom Pricing allows you to create Quantity Breaks discounts for both logged-in and non-logged in customers. You can offer one set of Quantity Break discounts for all customers (non-logged in) and another set for logged-in (and tagged) customers.