Any tips/tricks to copy a 'rounded-off' decimal vale into a text field.

I am aware that .. a formula cannot work cross-datatype. i.e. a numeric (decimal value) cannot be used/copied/auto-populated into a text field. But are there any tricks that can do this.

We have a typical requirement where users enter a decimal value into one of the fields and this value (rounded to the nearest) has to be used in a hyperlink picker (Type = string)

So . .I am exploring:

1. How do i round off a decimal value to its nearest

2. how do i copy/store that value into a string field (text box)