Type your entire sum into a calculator and press equals.
1. Write out that answer with just two numbers after the decimal point e.g. 52387.6680923 would be written as 52, 387.67 as the third number is rounded up or down.
2. Round your number to the nearest 100. 52387.6680923 to the nearest hundred is 524 hundred, also known as 52400.
If you were supposed to do this in your head, gl.