Edit in JSFiddle

var myApp = angular.module("myApp", []);

myApp.service('itemService', function () {
    return {
        name: undefined,
        price: 0,
        getItemName: function () {
            return this.name;
        },
        priceWithTax: function (tax) {
            return Math.floor(this.price * tax);
        }
    };
});

myApp.controller("myCtrl1", ['$scope', 'itemService', function ($scope, itemService) {
    $scope.itemService = itemService;
}]);

myApp.controller("myCtrl2", ['$scope', 'itemService', function ($scope, itemService) {
    $scope.itemService = itemService;
}]);

<div ng-app="myApp">
    <div ng-controller="myCtrl1">
        <p>商品名</p>
        <input type="text" ng-model="itemService.name"></input>
        <p>税別価格(円)</p>
        <input type="text" ng-model="itemService.price"></input>
        <p>※以下の税込価格は1円未満は切捨てです。</div>
    <hr>
    <div ng-controller="myCtrl2">
         <h3>2014/3/31までの税込価格</h3>

        <p>商品名 = {{itemService.getItemName()}}</p>
        <p>商品価格(税込5%) = {{itemService.priceWithTax(1.05)}}</p>
        <hr>
         <h3>2014/4/1から2015/9/30までの税込価格</h3>

        <p>商品名 = {{itemService.getItemName()}}</p>
        <p>商品価格(税込8%) = {{itemService.priceWithTax(1.08)}}</p>
        <hr>
         <h3>2015/10/1からの税込価格</h3>

        <p>商品名 = {{itemService.getItemName()}}</p>
        <p>商品価格(税込10%) = {{itemService.priceWithTax(1.10)}}</p>
    </div>
</div>