import { Temporal } from "@js-temporal/polyfill";
/**
 * Round an ISO 8601 time string to the specified time unit.
 *
 * - Returns "" for invalid inputs.
 * - Only time units are accepted: "hour", "minute", "second", "millisecond", "microsecond", "nanosecond".
 * - Wraps Temporal.PlainTime.round() which throws on invalid options.
 *
 * @param value ISO 8601 time string
 * @param options Rounding options: smallestUnit, optional roundingIncrement and roundingMode
 * @returns Rounded ISO 8601 time string, or "" on invalid input
 *
 * @example roundTime("12:34:56", { smallestUnit: "hour" }) // "13:00:00"
 * @example roundTime("12:34:56", { smallestUnit: "minute" }) // "12:35:00"
 * @example roundTime("12:34:56", { smallestUnit: "second", roundingMode: "floor" }) // "12:34:56"
 * @example roundTime("invalid", { smallestUnit: "hour" }) // ""
 */
export declare function roundTime(value: string, options: {
    smallestUnit: Temporal.SmallestUnit<"hour">;
    roundingIncrement?: number;
    roundingMode?: Temporal.RoundingMode;
}): string;