10493.3333333 need to round to nearest dollar amount if at $0.50 needs to round up anything less round down

Did you try Math.round()?

Have you tried setting the number of decimal places for the field so the value displays as whole dollars only?

Note the above does not change the value of the field. To change the value  of the field, you will need to round the computed value of the field in your calculation. The value of the field and not the displayed value is used in subsequent calculations.