ROUNDUP / ROUNDDOWN — DAX function reference

Round away from / toward zero.

Syntax

dax

ROUNDUP(<number>, <num_digits>)    ROUNDDOWN(<number>, <num_digits>)

dax

ROUNDUP([Sales], 0)

→ A number

dax

ROUNDUP(DIVIDE(COUNTROWS(Sales), 50), 0)

→ Number of pages needed at 50 rows per page, always rounding up

dax

ROUNDDOWN([Discount %] * 100, 0) / 100

→ Truncates a discount percentage to a whole percent, never rounding up

ROUNDUP always moves away from zero and ROUNDDOWN always moves toward zero, regardless of sign — ROUNDDOWN(-4.7, 0) is -4, not -5, which is easy to get backwards with negative numbers.
Neither performs "normal" rounding to the nearest value — using ROUNDUP/ROUNDDOWN where ROUND was intended is a common off-by-a-cent bug in financial measures.

From Math & statistics