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	$71.66	4.307%	$74.7464	$74.75	$74.75	$74.70
Purchase #2	$128.56	10.786%	$142.4265	$142.43	$142.45	$142.40
Purchase #3	$182.52	12.624%	$205.5613	$205.56	$205.55	$205.60
Purchase #4	$63.28	13.849%	$72.0436	$72.04	$72.05	$72.00
Purchase #5	$243.52	13.178%	$275.6111	$275.61	$275.60	$275.60
Purchase #6	$165.40	6.456%	$176.0782	$176.08	$176.10	$176.10
Purchase #7	$101.26	10.289%	$111.6786	$111.68	$111.70	$111.70
7 purchase totals =	$956.20		$1,058.1457	$1,058.15	$1,058.20	$1,058.10