Format type: 'quantitative' so that it looks something like '$1.1M'

[ghost]

Hi All
I am stuck with a formatting issue in vega-lite where I have requirement something like $600k,$700K.....$1.0M, $1.1M. So I m using format: '$~s' which is solving my problem but I want to restrict decimal point to 1. I am trying to use expressionFunction which I found here https://vega.github.io/vega-lite/docs/config.html . But looks like this is also not working.
Any suggestions. How to get the expected results with formatting? I have also tried creating my own custom labels and pass it to specs but it created a whole lot of problems.

Any suggestions will be appreciated.
Thank you in advance