setlength(...)
a:=pos('.',str);if  str[a+2] <> '0' then
   begin
     str[a+2]:='0';
        if str[a+1]='9' then  begin 
                        str[a-1]:=chr(ord(str[a-1])+1)
                         str[a+1]:='0'; 
                        end;
     str[a+1]:=chr(ord(str[a+1])+1);
   end;可能会有点问题,没试过