I found this article discussing implementation of different Linked List features in JS. It also pointed me to a Wikipedia article on this subject.

Thanks for the translation!

Depends on whether the number rounded up to integer is closer to nearest integer ending with 0 or with 5.
E.g. 12.5 rounds up to 13, so the output for this will be 15, while 12.4 rounds up to 12 and the result will be 10.

Thank you for catching that! Function name came from template.