How can I round up the users input to the next thousand using javascript?

<FORM name="rateform">
      <p align="left"><b><font size=2 face="Verdana" color="#006600"> Enter Policy Amount</font></b> <br />
                  <br />
                  <INPUT name=insurance size="35" style=background-color: #FFFFFF; border: 1px inset #C0C0C0; font-size:11px; onblur="this.value=1000*Math.round(this.value/1000+1)">
</TR>
      <p align="left"><font size=1 face="Verdana">Do not enter any 
                currency symbols or commas<br>
                </FONT>                
      <p align="left"><font color="#006600" size="2" face="Verdana">
                <input onclick=calculateRate(); type=button value="Calculate Base Premium:" name=calculate_rate style="border:1px solid #006600; font-family: Arial; font-size: 8pt; background-color: #81AA71; color:#FFFFFF; font-weight:bold" />
                </font>
      <p align="left"><b> <font size=2 face="Verdana" color="#006600">Base Premium</font></b>
                    </TD>
        <br />
                    <br />
                    <INPUT size=35 value=0 name=Loan_Policy style="border: 1px inset #C0C0C0; font-size:11px"></TD>
                  
                    <script language=JavaScript>
 
 
function calculateRate(){
  var insurancevalue;
  var loan_Policy = "";
 
  insurancevalue = document.rateform.insurance.value;
  loan_Policy = basic_premium(insurancevalue);
 
    document.rateform.Loan_Policy.value = "$" + loan_Policy;
 
}
     
function basic_premium(value){
  var premium;
  var overmin;
 
 
 
    
    
  function  validateNumeric( strValue ) {
  var objRegExp  =  /^[0-9]*$/;
 
  //check for numeric characters
  return objRegExp.test(strValue);
}
 
if( !validateNumeric(value))
	    { premium = alert("Please enter the value in whole dollar ammount without commas or decimals");
      window.location.href = "titlefee-loan2.shtml";
    }   
    
 if( !validateNumeric(value))
	    { premium = 0;
    }   
 
 
	else if ( (value >= 1) & (value <= 16000) )
       {  overmin = ((50)); 
       premium = (overmin);
    }
	else if ( (value >= 16001) & (value <= 17000) )
       {  overmin = ((51)); 
       premium = (overmin);
    }
	else if ( (value >= 17001) & (value <= 49999) )
    {  overmin = ((value)); 
       premium = (overmin*.003)-3;
    }
	else if ( (value >= 50000) & (value <= 50000) )
    {  overmin = ((value)); 
       premium = (overmin*.003)-3;
    }
	else if ( (value >= 50001) & (value <= 99999) )
    {  overmin = ((value)); 
       premium = (overmin*.0025)+25;
    }
	else if ( (value >= 100000) & (value <= 100000) )
    {  overmin = ((value)); 
       premium = (overmin*.0025)+25;
    }
	else if ( (value >= 100001) & (value <= 49999) )
    {  overmin = ((value)); 
       premium = (overmin*.002)+75;
    }
	else if ( (value >= 500000) & (value <= 500000) )
    {  overmin = ((value)); 
       premium = (overmin*.002)+75;
    }
	else if ( (value >= 500001) & (value <= 999999) )
    {  overmin = ((value)); 
       premium = (overmin*.00175)+200;
    }
	else if ( (value >= 10000000) & (value <= 10000000) )
    {  overmin = ((value)); 
       premium = (overmin*.00175)+200;
    }
 
 
	 var temp1 = (premium);
    
    var s1 = temp1.toString();
    var decimalExists = s1.indexOf('.')
     
    if(decimalExists == -2)
        s1 = s1+".00";
        
    else
  {  
    if( (s1.length - decimalExists) == 2) 
      s1 = s1+"0";
      
{
	
	}
	
}
    return s1
}
                    </script>
    </FORM>

                                  

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