Issue regarding value rounding

Hi, somewhat new to excel and having trouble with rounding.

I have a column of values I'm running through either an IF function or an IFS function, depending on complexity, to generate a percentage for customers. These values are imported from invoicing software and I need to make the calculated values match the values received from the software.

The problem I'm running into is when I use the SUM function to total the amounts for each column. Specifically, the total I get for the column of values derived from the IF and IFS functions is less than the value from the one imported from the invoicing software, because the calculated values aren't rounding up to the correct decimal. the SUM function appears to bypass whatever setting I make for the cell's decimals using the "increase decimal" or "decrease decimal" settings.

I'm aware that there are ROUND functions, but I don't want to have to create yet another column just to round up the values calculated from the IF/IFS columns. Is there a way to make the output from the latter round to the correct spot? Going through Microsoft's help pages seems to suggest I have to run everything through the ROUND functions, but surely that can't be my only option, right?

I need to keep this as simple as possible. The end goal with this project is to pass this file along to staff who can manipulate the variables of the IF/IFS functions on the imported values to explore results. Staff who have even less knowledge of excel than I do, and mine is pretty minimal already.

Thanks in advance!

EDIT: To be clear, I'm trying to avoid using =ROUND, specifically because I need to give this project to staff, so they can manipulate the results by changing values. The more complicated I make the equation, the more likely they are to break it when they need to change a parameter I didn't account for, giving me more work to do fixing it. (and likely blame for it not working right). If there is truly no other way, please let me know.