Jada is buying 4 stamps that cost $0.49 each. How can rounding be used to estimate the total cost of the stamps? Since each stamp is about $0.50, the total cost is approximately 4 + 0.5 = $4.50. Since she is buying about 10 stamps, the total cost is approximately 10 × 0.49 = $4.90. Since each stamp is about $0.50, the total cost is approximately 4 × 0.5 = $2.00. Since she is buying about 10 stamps, the total cost is approximately 10 + 0.49 = $10.49