47.488539642204628
truncates to: 47.488539
rounds to:    47.488540

##</code><code>##

use warnings;
use strict;

my $content = '{ "geometry": { "type": "Polygon", "coordinates": [ [ [ 19.054804912278406, 47.485785556135411 ], [ 19.057857836771483, 47.487322542030711 ], [ 19.06025597925397, 47.488491565765209 ], [ 19.060347248086835, 47.488539642204628 ], [ 19.060463310421543, 47.484578287406251 ], [ 19.054804912278406, 47.485785556135411 ] ] ] } }';

$content =~ s/(\d\d\.\d*)/sprintf("%.6f",$1);/ge; #round to 6 decimal digits
print "$content\n";

__END__
Truncated:
{ "geometry": { "type": "Polygon", "coordinates": [ [ [ 19.054804, 47.485785 ], [ 19.057857, 47.487322 ], [ 19.060255, 47.488491 ], [ 19.060347, 47.488539 ], [ 19.060463, 47.484578 ], [ 19.054804, 47.485785 ] ] ] } }

Rounded:
{ "geometry": { "type": "Polygon", "coordinates": [ [ [ 19.054805, 47.485786 ], [ 19.057858, 47.487323 ], [ 19.060256, 47.488492 ], [ 19.060347, 47.488540 ], [ 19.060463, 47.484578 ], [ 19.054805, 47.485786 ] ] ] } }