I can envisage having no tattoos, & being with someone who finds them repellent or objectionable somehow - as in, they'd have been a deal-breaker when the two of us got together - & so in these circumstances I probably wouldn't get one, even though I might rather like one, because 'not having tattoos' would be part of the understanding between myself & my partner.
I'm not saying that the partner in this situation gets to veto the tattoo; but they do get to say 'I don't want to be with a person who has tattoos - I've always felt like this, & you knew that when we got together, so if you do decide to get one, I'm off.'
But if OP already has 4, her dh obviously doesn't have any sort of tattoo-phobia - either he originally got together with a tattooed woman, or he's not objected to #1-4 in the course of the relationship. At this point he can disapprove of #5 all he likes, & again how he reacts is up to him, but he's hardly being reasonable to try to lay down the law!
I like my tattoo, & I'm planning more. The one I've got was originally a cover up of a faded one I had done at 18. The place I went to for the original cover up didn't do a particularly great job of it, & I've had it much improved by someone better since.
My tattoo's never been a problem in my rather responsible & respectable teaching job.
I'd be honestly bewildered if anyone did think it was something they could comment on negatively, tbh. It's fine if someone doesn't like it & wouldn't have one, but good manners surely require them to keep that opinion to themselves, exactly as I don't make rude remarks about, say, shellac nails or botoxed faces, despite privately thinking that both look ghastly.