Table grid glitches on certain zoom level

When writing tables in LaTeX I sometime notice with various PDF viewer the same glitches that only seem to appear on certain zoom level.

Any explanation?

Another example of these glitches, but this time in the opposite direction:

Here a minimal example (taken from here):

documentclass{article}
begin{document}

begin{table}
    caption{Table showing Feature 5's Functional Tests}
    hspace*{-0.5in}
    begin{tabular}[h!]{|p{0.6cm}|p{4cm}|p{5cm}|p{4cm}|p{1.5cm}|}
    hline
    {bf Test ID } & {bf Task } & {bf Expected} & {bf Actual} & {bf Outcome} 
    hline
       5.1 & Something &  Something & Something &  Success 
    hline
       5.2 & Something &  Something & Something &  Success 
    hline
       5.3 & Something &  Something & Something &  Success 
    hline
       5.4 & Something &  Something & Something &  Success 
    hline
    end{tabular}
    end{table}
end{document}

setlength{arrayrulewidth}{5pt}
begin{tabular}{|l|}
hline A  hline
end{tabular}