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	$158.77	6.157%	$168.5455	$168.55	$168.55	$168.50
Purchase #2	$65.59	9.690%	$71.9457	$71.95	$71.95	$71.90
Purchase #3	$132.60	9.188%	$144.7833	$144.78	$144.80	$144.80
Purchase #4	$208.70	4.162%	$217.3861	$217.39	$217.40	$217.40
Purchase #5	$52.28	10.807%	$57.9299	$57.93	$57.95	$57.90
Purchase #6	$56.29	13.612%	$63.9522	$63.95	$63.95	$64.00
Purchase #7	$30.78	13.161%	$34.831	$34.83	$34.85	$34.80
7 purchase totals =	$705.01		$759.3737	$759.38	$759.45	$759.30