[SalesForce] Rollup summary of currency field using Apex Trigger

I have written an Apex Trigger to perform the rollup summary(sum ) operation..In the image "Total order Item value" field will be populated using trigger. And "Total Order Items" populates the value based on rollup summary.
The problem here is. under Total order Item Value instead of considering user define currency value, it is taking default company value which show with arrow.

Total Order Item Value will depend on (Quantity * Sell price)which returns value in usd. I want the same USD value under this field instead of converted.

Let me know thoughts.
Here is the code:

Apex class:

public class RollUpSummaryUtility {

    //the following class will be used to house the field names
    //and desired operations
    public class fieldDefinition {
        public String operation {get;set;}
        public String childField {get;set;}
        public String parentField {get;set;}

        public fieldDefinition (String o, String c, String p) {
            operation = o;
            childField = c;
            parentField = p;
        }
    }

    public static void rollUpTrigger(list<fieldDefinition> fieldDefinitions,
    list<sObject> records, String childObject, String childParentLookupField, 
    String parentObject, String queryFilter) {

        //Limit the size of list by using Sets which do not contain duplicate
        //elements prevents hitting governor limits
        set<Id> parentIds = new set<Id>();

        for(sObject s : records) {
            parentIds.add((Id)s.get(childParentLookupField));
        }

        //populate query text strings to be used in child aggregrator and 
        //parent value assignment
        String fieldsToAggregate = '';
        String parentFields = '';

        for(fieldDefinition d : fieldDefinitions) {
            fieldsToAggregate += d.operation + '(' + d.childField + ') ' + 
            ', ';
            parentFields += d.parentField + ', ';
        }

        //Using dynamic SOQL with aggergate results to populate parentValueMap
        String aggregateQuery = 'Select ' + fieldsToAggregate + 
        childParentLookupField + ' from ' + childObject + ' where  ' + 
        childParentLookupField + ' IN :parentIds ' + queryFilter + ' ' +
        ' group by ' + childParentLookupField;

        //Map will contain one parent record Id per one aggregate object
        map<Id, AggregateResult> parentValueMap = 
        new map <Id, AggregateResult>();

        for(AggregateResult q : Database.query(aggregateQuery)){
            parentValueMap.put((Id)q.get(childParentLookupField), q);
        }

        //list of parent object records to update
        list<sObject> parentsToUpdate = new list<sObject>();

        String parentQuery = 'select ' + parentFields + ' Id ' +
         ' from ' + parentObject + ' where Id IN :parentIds';

        //for each affected parent object, retrieve aggregate results and 
        //for each field definition add aggregate value to parent field
        for(sObject s : Database.query(parentQuery)) {

            Integer row = 0; //row counter reset for every parent record
            for(fieldDefinition d : fieldDefinitions) {
                String field = 'expr' + row.format();
                AggregateResult r = parentValueMap.get(s.Id);
                //r will be null if no records exist 
                //(e.g. last record deleted)
                if(r != null) { 
                    Decimal value = ((Decimal)r.get(field) == null ) ? 0 : 
                        (Decimal)r.get(field);
                    s.put(d.parentField, value);
                } else {
                    s.put(d.parentField, 0);
                }
                row += 1; //plus 1 for every field definition after first
            }
            parentsToUpdate.add(s);
        }

        //if parent records exist, perform update of all parent records 
        //with a single DML statement
        if(parentsToUpdate.Size() > 0) {
            update parentsToUpdate;
        }

    }

}

Trigger:

trigger GT_TotalOrderItem on OSF_Order_Items__c (after delete, after insert, 
after update, after undelete) {

    if(trigger.isInsert || trigger.isUpdate || trigger.isUnDelete){

        list<RollUpSummaryUtility.fieldDefinition> fieldDefinitions = 
        new list<RollUpSummaryUtility.fieldDefinition> {
            new RollUpSummaryUtility.fieldDefinition('SUM', 'Total_Selling_Price__c', 
            'Test_Total_Order_Item__c')
             };

        RollUpSummaryUtility.rollUpTrigger(fieldDefinitions, trigger.new, 
        'OSF_Order_Items__c', 'Opportunity__c', 'Opportunity', '');

    }

    if(trigger.isDelete){

        list<RollUpSummaryUtility.fieldDefinition> fieldDefinitions = 
        new list<RollUpSummaryUtility.fieldDefinition> {
            new RollUpSummaryUtility.fieldDefinition('SUM', 'Total_Selling_Price__c','Test_Total_Order_Item__c')

            };

        RollUpSummaryUtility.rollUpTrigger(fieldDefinitions, trigger.old, 
        'OSF_Order_Items__c', 'Opportunity__c', 'Opportunity', '');

    }

}