How to customize an individual axis tick

If you can't find a better solution, you could manually modify the scale like in this example.
Note: Please make your questions providing a REPRoducible EXample (reprex) like the one below.

library(tidyverse)
set.seed(1)
df <- data.frame(year = seq(1950, 2010, 10),
                 value = rnorm(7))

df %>% 
    ggplot(aes(year, value)) +
    geom_line() +
    scale_x_continuous(breaks = seq(1950, 2010, 10),
                       labels =str_replace(as.character(df$year), "^\\d{2}(?!(5|0))", "'")) +
    theme_minimal()

Created on 2019-09-12 by the reprex package (v0.3.0.9000)

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