You can examine the current coverage in your simulation 9using the get_coverage method) and when it reaches 100% then just issue $finish
e.g.
if (seq_coverage.seq_2_seq.get_coverage()==100.0)
begin
$write("Sequence coverage = %6.2f, ", seq_coverage.seq_2_seq.get_coverage());
$display("Total coverage = %6.2f", seq_coverage.get_coverage());
$finish();
end