  Let $A/\mathbb{Q}$ be a Jacobian variety and let $F$ be a totally real,
tamely ramified, abelian number field. Given a character $\psi$ of
$F/\mathbb{Q}$, Deligne's Period Conjecture asserts the algebraicity of the
suitably normalised value $\mathcal{L}(A,\psi,1)$ at $z=1$ of the
Hasse-Weil-Artin $L$-function of the $\psi$-twist of $A$. We formulate a
conjecture regarding the integrality properties of the family of normalised
$L$-values $(\mathcal{L}(A,\psi,1))_{\psi}$, and its relation to the
Tate-Shafarevich group of $A$ over $F$. We numerically investigate our
conjecture through $p$-adic congruence relations between these values.
