If the number you are rounding is followed by 5, 6, 7, 8, or 9, round the number up (+1).
If the number you are rounding is followed by 0, 1, 2, 3, or 4, round the number down (no change).
3,422,087 ≈ 3,422,000
19,499,890 ≈ 19,000,000
507,378 ≈ 1,000,000
207,689 ≈ 210,000