You should be fine.
RS-485 does specify signal levels of ±1.5V5 V to ±5V±5 V, but even so, and even when the sensor would misbehave or when the common mode voltage is low or high, there is still the TTL-to-RS485 converter in the middle that has 5V5 V TTL logic on the Arduino side.
As long as the TTL-to-RS485 converter is properly connected to the Arduino and working as it should, the Arduino is safe.