is there a formula to round down automatically a number with or without comma?

i'd like the formula to take the value from a cell (for example A1) and round that number down (B1)

if A1 is 229, the value of B1 has to be 220

if A1 is 373.20, B1 is 370

i'm not that good with this stuff so i don't know if it's possible to do something like this.