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	$59.94	7.627%	$64.5116	$64.51	$64.50	$64.50
Purchase #2	$153.96	9.500%	$168.5862	$168.59	$168.60	$168.60
Purchase #3	$33.48	3.290%	$34.5815	$34.58	$34.60	$34.60
Purchase #4	$55.90	10.826%	$61.9517	$61.95	$61.95	$62.00
Purchase #5	$33.68	3.492%	$34.8561	$34.86	$34.85	$34.90
Purchase #6	$50.80	4.286%	$52.9773	$52.98	$53.00	$53.00
Purchase #7	$150.26	13.180%	$170.0643	$170.06	$170.05	$170.10
7 purchase totals =	$538.02		$587.5287	$587.53	$587.55	$587.70