In order to communicate with docker running inside docker toolbox, we must install the CA into the trusted root CA certificate store in the form of a pfx. By default, docker toolbox provides pem files, which can be converted into pfx easily.
Go to %UserProfile%\.docker\machine\certs
Once there, convert the CA and cert files to pfx as below.
openssl pkcs12 -export -inkey ca-key.pem -in ca.pem -out ca.pfxopenssl pkcs12 -export -inkey key.pem -in cert.pem -out key.pfx
Double click on the ca.pfx file, and install it into the trusted root CA store.