This seems to work:

ndp(fpn,dp):=float(round(fpn*10^dp)/10^dp)$

e.g.

(%i4)   kill(all)$
    ndp(fpn,dp):=float(round(fpn*10^dp)/10^dp)$
    for i :1 thru 10 do (
        fpnArray[i]:10.01+i/1000,
        anArray[i]:ndp(fpnArray[i],2));
    listarray(fpnArray);
    listarray(anArray);
(%o2)   done

(%o3)   [10.011,10.012,10.013,10.014,10.015,10.016,10.017,10.018,10.019,10.02]

(%o4)   [10.01,10.01,10.01,10.01,10.02,10.02,10.02,10.02,10.02,10.02]