To find the total number of 7-digit numbers whose sum of digits is even, we need to consider the possible values for each digit.

1. Analyzing the units digit:
- The units digit can be any digit from 0 to 9.
- Since we need the sum of digits to be even, we can choose any digit except for 9, as the sum of a 7-digit number with 9 as the units digit will always be odd.
- Therefore, we have 9 choices for the units digit.

2. Analyzing the tens digit:
- The tens digit can also be any digit from 0 to 9.
- Since the sum of digits is even, we need to choose a digit that will make the sum even when added to the units digit.
- If the units digit is even, we can choose any digit. There are 10 choices in this case.
- If the units digit is odd, we need to choose an even digit. There are 5 choices in this case (0, 2, 4, 6, 8).

3. Analyzing the remaining digits:
- For each of the remaining five digits, we can choose any digit from 0 to 9 (10 choices) since the sum of digits will always remain even.

4. Calculating the total number of 7-digit numbers:
- By multiplying the choices for each digit, we can calculate the total number of 7-digit numbers.
- Total = (9 choices for units digit) * (10 choices for tens digit) * (10 choices for each of the remaining five digits)
- Total = 9 * 10 * 10 * 10 * 10 * 10 * 10 = 9000000

Therefore, the correct answer is option B) 4500000.