Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$168.39	12.416%	$189.2973	$189.30	$189.30	$189.30
Purchase #2	$14.83	4.803%	$15.5423	$15.54	$15.55	$15.50
Purchase #3	$91.89	11.201%	$102.1826	$102.18	$102.20	$102.20
Purchase #4	$116.25	13.203%	$131.5985	$131.60	$131.60	$131.60
Purchase #5	$39.55	9.335%	$43.242	$43.24	$43.25	$43.20
Purchase #6	$158.52	12.719%	$178.6822	$178.68	$178.70	$178.70
Purchase #7	$131.94	10.783%	$146.1671	$146.17	$146.15	$146.20
7 purchase totals =	$721.37		$806.7120	$806.71	$806.75	$806.70