According to APMEX FAQ section, Silver Eagles and Silver Rounds are not taxable when you sell.
The IRS has specific rules related to reportable transactions that require a Form 1099-B to be filed and those rules are included in the Form 1099-B instructions on the IRS website. The following are guidelines provided by ICTA related to Precious Metal sales, and these guidelines, as well as the IRS rules, are subject to change at any time without notice.
Reportable Item
Minimum Fineness
Minimum Reportable Amount
Gold Bars
0.995
Any size bars totaling 1 Kilo (32.15 troy oz) or more
Silver Bars
0.999
Any size bars totaling 1000 troy oz or more
Platinum Bars
0.995
Any size bars totaling 25 troy oz or more
Palladium Bars
0.9995
Any size bars totaling 100 troy oz or more
Gold 1 oz Krugerrand
as minted
Twenty-five (25) 1 oz coins
Gold 1 oz Maple Leaf
as minted
Twenty-five (25) 1 oz coins
Gold 1 oz Mexican Onza
as minted
Twenty-five (25) 1 oz coins
U.S. 90% Silver Coins
as minted
Any combination of dimes, quarters, or half-dollars totaling $1,000 face value or more