To find the number of cartons needed, we divide the total number of toys by the capacity of each carton: $45678 \div 100 = 456.78$. The question asks to round this to the nearest whole number of cartons. To round $456.78$ to the nearest whole number, we look at the digit in the tenths place, which is 7. Since 7 is 5 or greater, we round up the ones digit. Therefore, $456.78$ rounded to the nearest whole number is 457 cartons.