In column A I have:
70,512,777
79,462,672
9,360,902
2,870,540
264,100
121,022
162,592,013 Total
In column B I display the number in thousands
70,513
79,463
9,361
2,871
264
121
162,592 Total If you add down the number in column B the answer is
162,593. So I am going into the cell that contains 2,871 and changing it to
2,870 and then increasing the cel that contains 162,593 to 162,592 so that it
will match the total in column A. Depending on the numbers, I sometimes have
to increase a number up or down.

You shouldn't need to add the numbers displayed in thousands. Just put
the rounded total from column A into column B. Note somewhere that
totals may be different from the underlying numbers due to rounding
issues.