Fix in Calculator::GetPriceForTimeStep():

Allow some tolerance (of 3 minutes) when looking up the
	current time-step value in the duration-array.
	Otherwise, when corossing a minute-boundary, it can happen to
	not find the match and returning a price of 0 (which is almost
	always wrong).

library/src/calculator_functions.cpp

@@ -458,7 +458,7 @@ Calculator::ComputeDurationFromCost(Configuration *cfg,
                                                         arg(cost).arg(nettoParktimeForCost);
 
     int cnt = 0;
-    while (++cnt < 10 && netto_parking_time_in_minutes < nettoParktimeForCost) {
+    while (++cnt < 20 && netto_parking_time_in_minutes < nettoParktimeForCost) {
         // qCritical() << __func__ << ":" << __LINE__ << "cnt [" << cnt;
 
         brutto_parking_time_in_minutes = free_parking_time_in_minutes + netto_parking_time_in_minutes;
@@ -3584,7 +3584,9 @@ uint32_t Calculator::GetPriceForTimeStep(Configuration *cfg, int timeStep, int p
             qCritical() << "(" << __func__ << ":" << __LINE__ << ") timeStep" << timeStep;
         }
 
-        if (timeStep == pun_duration) {
+        // allow some tolerance when searching for [timeStep == pun_duration]:
+        // this might happen when crossing minute boundaries
+        if (std::abs(timeStep - pun_duration) < 4) {
             qCritical() << "(" << __func__ << ":" << __LINE__ << ") return price" << price;
             return price;
         }