A tip or gratuity is an amount of money that is given to a worker such as a waiter or
waitress who performs a service for you. A common tip amount is 15% of the cost of
the meal or other service. Generally a tip is determined based on the total bill
which includes the cost of the meal and sales tax.

If a meal costs $10.00 and sales tax is 5% the bill is $10.50. A 15% tip based
on the $10.50 cost would be $1.58. The total would be $10.50 + $1.58 = $12.08.

To estimate the amount of a tip round the total bill to the most significant
place value. A $16.75 meal would round to $20. Next, move the decimal point of the
rounded amount one place to the left. This will be 10% of the total cost.
Next divide this amount in half to determine 5%. Add the 10% amount and the 5%
amount together to estimate 15% of the total. In this case, it would be a
$2.00 + $1.00 = $3.00 tip.