customise y axis and x axis tick marks

is there a way to further customise the tick marks on the y and x axis? And can there be major and minor tick marks? For example that it shows the value with a big tick mark on the y axis every 10000 step and a small tick mark every 5000 step? And for the x axis that it would only show every fifth year for example? For the y axis I tried doing this with seq() but it changed the scaling and did not show all the tick marks...