The contingency table does not appear to be editable (I work in JMP 9 for Mac) but you can export it into a data table by selecting "make into data table" from under the red triangle. The nr of decimals can then be set for the columns. This can also be scripted as in the example below (the first part borrrowed from the example found in Help/Displaybox Scripting/CrossTabBox).
Open( "$ENGLISH_SAMPLE_DATA/Alcohol.jmp" );
c = Contingency(
Y( :Relapsed ),
X( :Alcohol Consumption ),
Freq( :Count ),
Contingency Table(
Count( 1 ),
Total %( 1 ),
Col %( 1 ),
Row %( 1 ),
Expected( 0 ),
Deviation( 0 ),
Cell Chi Square( 0 ),
Col Cum( 0 ),
Col Cum %( 0 ),
Row Cum( 0 ),
Row Cum %( 0 )
)
);
cr = c << report;
ctb = cr[CrosstabBox( 1 )];
Print( ctb << Get As Matrix );
dt=ctb << make into datatable;
for(i=1, i<= ncol(dt), i++, if ((column(dt,i)<<get data type)=="Numeric",column(dt,i)<< format("fixed dec",0)));