I want to round a number down to three decimal places and have tried
rounddown, floor and trunc but I keep getting an unintended result in the
following situation:

If my number is 0.3021 i want to return 0.302
If my number is 0.3027 i want to return 0.302
If my number is 0.3020 i want to return 0.302, but I keep getting 0.301

All of these give me 0.301 when the fourth decimal place is a zero.
ROUNDOWN(cell,3)
FLOOR(cell,0.001)
TRUNC(cell,3)