Ngram indicates was established to is more prevalent than was founded to. It might be argued that founded inclines slightly more towards the (corporate) structure and established slightly more towards the principles, but it's a fine line.
More important than "formed" or "founded" in this specific example is this: "The supermarket where I work opened in May, 1999." When or how it was formed or founded is generally irrelevant, unless you are legally referring to when the organization that owns and operates the supermarket was incorporated, in which case that is the correct term to use. In the non-profit sector, I would say that ...
word choice - "Founded on [date]" vs. "Founded in [date]" - English ...
In the sentences below: Quora was established in 2009. Quora was founded in 2009. They seem interchangeable in the sentences above. I was told that 'found' was informal form of 'establish', is that
9 A business founded (or a building built or a monument dedicated) in 1854 might have a sign or plaque reading "EST'D 1854" or "EST 1854" or "ESTD 1854", or some other combination I haven't seen or heard of. What is the correct way to abbreviate the word "established" in this manner? What is the correct way to capitalize this abbreviation?
If found is regular (which the past tense founded suggests), then it will have an infinitive form found, which will be grammatical after the to complementizer. The verb plan can take practically any infinitive clause with Equi-Subject like this (i.e, same subject of plan and found), provided the verb is one that can have a human subject.