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	$64.38	5.578%	$67.9711	$67.97	$67.95	$68.00
Purchase #2	$44.77	11.380%	$49.8648	$49.86	$49.85	$49.90
Purchase #3	$175.76	4.176%	$183.0997	$183.10	$183.10	$183.10
Purchase #4	$59.47	3.202%	$61.3742	$61.37	$61.35	$61.40
Purchase #5	$38.72	4.406%	$40.426	$40.43	$40.45	$40.40
Purchase #6	$65.71	7.837%	$70.8597	$70.86	$70.85	$70.90
Purchase #7	$247.43	6.675%	$263.946	$263.95	$263.95	$263.90
7 purchase totals =	$696.24		$737.5415	$737.54	$737.50	$737.60