Write a Python function `is_decimal` that checks whether a given string represents a decimal number with a precision of up to 2 decimal places. The function should return `True` if the string is a valid decimal number with at most two digits after the decimal point, and `False` otherwise.
#### Requirements:
- The input will be a string.
- A valid decimal number can have:
- Only digits (e.g., `"123"` is valid).
- A decimal point followed by up to two digits (e.g., `"123.45"` is valid).
- No leading or trailing spaces.
- No additional characters or multiple decimal points.
#### Examples:
```python [main.nopy]
is_decimal("123.11") # True
is_decimal("e666.86") # False
is_decimal("3.124587") # False
is_decimal("1.11") # True
is_decimal("1.1.11") # False
```
Implement the function to meet these requirements.