Skip to main content
The Centsless engine resolves the correct rounding rule for any merchant location using a hierarchical cascade: city, county, state, then federal default. This ensures that if a city or county enacts a more specific rule than the state, the most local rule applies. You do not need to manage this logic yourself — the engine handles the full resolution chain automatically.

​
Resolution cascade

When you submit a transaction or a standalone lookup, the engine checks each level in order and returns the first match: 
ZIP Code (85001)
  -> City (Phoenix)
    -> County (Maricopa)
      -> State (Arizona)
        -> Federal (default)

​
Three integration paths

Send the merchant’s ZIP code. The engine resolves the full location chain automatically using a Census database of 33,791 U.S. ZIP codes — no address parsing required on your side. 
{
  "merchant_id": "MERCHANT-001",
  "subtotal_cents": 523,
  "tax_total_cents": 200,
  "payment_method": "cash",
  "zip_code": "85001"
}

​
Path 2: State, county, and city

Send the location components directly. Use this path when your POS already has structured address data and you want explicit control over the resolution inputs. 
{
  "merchant_id": "MERCHANT-001",
  "subtotal_cents": 523,
  "tax_total_cents": 200,
  "payment_method": "cash",
  "state": "AZ",
  "county": "Maricopa",
  "city": "Phoenix"
}

​
Path 3: Explicit override

Send the rounding mode and jurisdiction directly. Use this path for testing, development, and edge case handling where you need to force a specific rounding behavior regardless of the merchant’s location. 
{
  "merchant_id": "MERCHANT-001",
  "subtotal_cents": 523,
  "tax_total_cents": 200,
  "payment_method": "cash",
  "cash_rounding_mode": "swedish_rounding",
  "jurisdiction": "US-AZ"
}

​
Standalone ZIP lookup

You can resolve a ZIP code without processing a transaction. This is useful for pre-validating a merchant location at onboarding time or displaying compliance information in your POS UI. 
curl https://api.centsless.org/api/v1/jurisdiction/zip/85001 \
  -H "x-api-key: YOUR_API_KEY"
The response includes the full resolution chain: state, county, city, rounding mode, enforcement level, and legislation reference.

​
Coverage

The jurisdiction database currently covers:
  • 33,791 ZIP codes mapped to state, county, and city
  • 6 enacted states with active rounding legislation
  • 55+ bills tracked across 35+ states with pending or proposed legislation
  • Automatic updates when new legislation is enacted
You do not need to redeploy or update your integration when new state legislation is enacted. The jurisdiction database updates automatically, and all in-flight transactions immediately reflect the new rules.