Colorado: Special Districts with Additional Use Tax

I'm a new CO resident and need help understanding this. The "Learn More" states

 

"Consumer use tax is tax on online or out-of-state purchases where you did not pay Colorado sales tax to the seller. Enter the total of all online and out-of-state purchases where a Colorado sales tax was not paid and the program will calculate the Colorado use tax for you."

 

Is this saying that I should have kept track of all online purchases, their amounts, and whether they included state tax? I don't have this information. I've made purchases from Amazon, Ebay, etc., and I assume that they collect appropriate taxes. Can I put zero here?

 

It would seem overly burdensome to have to poor through every single online purchase from the past year to see whether state tax was collected.

 

Update: tax.colorado.gov indicates that "Taxpayers may confidentially and without fear of criminal prosecution report zero on the use tax line of their individual income tax return." So I'm inclined to leave it blank.