use BigNumber

src/utils/fiatConverter.js

@@ -1,17 +1,19 @@
+import BigNumber from 'bignumber.js';
+
 const toFiatCurrency = (amount, fiatCurrency, rates) => {
     // calculate amount in local currency
     const rate = rates[fiatCurrency];
 
-    let localAmount = parseFloat(amount) * rate;
-    localAmount = Number.isNaN(localAmount) ? '' : localAmount.toFixed(2);
+    let localAmount = BigNumber(amount).times(rate);
+    localAmount = localAmount.isNaN() ? '' : localAmount.toFixed(2);
     return localAmount;
 };
 
 const fromFiatCurrency = (localAmount, fiatCurrency, rates, decimals) => {
     const rate = rates[fiatCurrency];
 
-    let amount = parseFloat(localAmount) / rate;
-    amount = Number.isNaN(amount) ? '' : amount.toFixed(decimals);
+    let amount = BigNumber(localAmount).div(rate);
+    amount = amount.isNaN() ? '' : amount.toFixed(decimals);
     return amount;
 };