In W.97 (& presumably the later versions) there's a decimal point tab alignment option.
Make sure you have the rulers displayed. At the far left side of the ruler will be a small box with an 'L', backwards 'L', upside down 'T' or upside down 'T' with a dot.
Each time you click on the icon it will cycled through to the next in the series. Each one represents a type of tab stop.
L = left aligned tab stop
backwards L = right aligned tab stop
inverted T = centre aligned tab stop
inv. T & dot = decimal point aligned tab stop.
Select the cells you wish to have tab aligned. Cycle through the tab types until the 'inv. T & dot' shows. In the ruler bar click on the position where you'd like the decimal point tab stop to occur.
You've now set a decimal point tab stop for each of the highlighted cells. Character to the left of a . will fill in to the left, characters to the right of a . will fill in to the right. No . acts as if there are no characters to the right of the decimal.