title: SwiftUI TextField FormatStyle rounding issue
body: <p>SwiftUIs TextField seems to have a rounding issue when changing the fractionalLength parameter. Someone knows how to fix it?</p>
  <p>Example:</p>
  <p>Entering <code>3.7777</code> after losing focus the value will be rounded to <code>3.8</code>. Increasing the fractionalLength to 2 decimals and entering <code>3.7777</code> after losing the focus the value will be rounded to <code>3.80</code>. The expectation would be <code>3,78</code>.</p>
  <p>The View:</p>
  <pre class="lang-swift prettyprint-override"><code>struct ContentView: View {
  
      enum FocusField: Hashable {
          case value
      }
  
      @State var value: Double?
      @State var decimals: Int = 1
  
      @FocusState private var focusedField: FocusField?
  
      var body: some View {
          List {
              TextField(&quot;Placeholder&quot;, value: $value, format: .number.precision(.fractionLength(decimals)))
                  .keyboardType(.decimalPad)
                  .focused($focusedField, equals: .value)
              Stepper(&quot;Decimals \(decimals)&quot;, value: $decimals, in: 1 ... 10)
          }
          .toolbar {
              ToolbarItemGroup(placement: .keyboard) {
                  Button {
                      focusedField = nil
                  } label: {
                      Text(&quot;Done&quot;)
                  }
              }
          }
      }
  }
  </code></pre>