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	$168.47	4.859%	$176.656	$176.66	$176.65	$176.70
Purchase #2	$153.29	3.714%	$158.9832	$158.98	$159.00	$159.00
Purchase #3	$95.50	13.629%	$108.5157	$108.52	$108.50	$108.50
Purchase #4	$49.92	5.451%	$52.6411	$52.64	$52.65	$52.60
Purchase #5	$95.43	10.746%	$105.6849	$105.68	$105.70	$105.70
Purchase #6	$18.89	5.314%	$19.8938	$19.89	$19.90	$19.90
Purchase #7	$142.56	6.807%	$152.2641	$152.26	$152.25	$152.30
7 purchase totals =	$724.06		$774.6388	$774.63	$774.65	$774.70