Truncating currency amounts – any guidelines?

I'm working on a large enterprise level financial application that has a requirement to display currency totals on a dashboard. The goal for these totals is to highlight the relative importance of one dashboard item over another (based on the total values).

Since we deal with some extremely large dollar values (frequently in the billions), we will potentially run into real estate issues when we render these dollar amounts. The ask from our stakeholders is to truncate the dollar values using some sort of notation. The suggestion is to truncate millions with 'M' and thousands with 'K'. For example, $984,432.00 would be rendered as $984K and $894,876,451 would be rendered as $894M.

My worry is that we're introducing too great a cognitive load on our users when they compare these currency values. In some cases, they will have to evaluate numbers only with values containing numbers as well as characters. My concerns may be completely irrational, but either way I would love to hear any thoughts anyone has with respect to this.