Fix price formatting for display of model total cost

[reddog]

Fix display of model total cost to show whole dollar value or with two decimal place cent value.

Currently, if calculated model cost is:

• a whole dollar value, it is showed without decimals, e.g. $60
• a decimal cent value with non-zero penny value, it is showed as two decimal places, e.g. $3.25
• a decimal cent value with zero penny value, it is showed incorrectly as one decimal place, e.g. $6.7

This fix correctly displays values either as whole dollars or with two decimal places.