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	$100.60	10.147%	$110.8079	$110.81	$110.80	$110.80
Purchase #2	$40.40	11.239%	$44.9406	$44.94	$44.95	$44.90
Purchase #3	$35.82	4.455%	$37.4158	$37.42	$37.40	$37.40
Purchase #4	$147.32	5.238%	$155.0366	$155.04	$155.05	$155.00
Purchase #5	$178.77	9.733%	$196.1697	$196.17	$196.15	$196.20
Purchase #6	$20.41	3.119%	$21.0466	$21.05	$21.05	$21.00
Purchase #7	$115.34	8.772%	$125.4576	$125.46	$125.45	$125.50
7 purchase totals =	$638.66		$690.8748	$690.89	$690.85	$690.80