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	$168.32	6.290%	$178.9073	$178.91	$178.90	$178.90
Purchase #2	$138.38	11.541%	$154.3504	$154.35	$154.35	$154.40
Purchase #3	$156.43	10.117%	$172.256	$172.26	$172.25	$172.30
Purchase #4	$30.97	3.654%	$32.1016	$32.10	$32.10	$32.10
Purchase #5	$56.58	10.819%	$62.7014	$62.70	$62.70	$62.70
Purchase #6	$134.84	8.617%	$146.4592	$146.46	$146.45	$146.50
Purchase #7	$13.30	11.527%	$14.8331	$14.83	$14.85	$14.80
7 purchase totals =	$698.82		$761.6090	$761.61	$761.60	$761.70