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	$75.51	12.635%	$85.0507	$85.05	$85.05	$85.10
Purchase #2	$85.38	7.455%	$91.7451	$91.75	$91.75	$91.70
Purchase #3	$51.58	9.292%	$56.3728	$56.37	$56.35	$56.40
Purchase #4	$101.88	9.699%	$111.7613	$111.76	$111.75	$111.80
Purchase #5	$57.36	6.395%	$61.0282	$61.03	$61.05	$61.00
Purchase #6	$122.25	12.565%	$137.6107	$137.61	$137.60	$137.60
Purchase #7	$156.87	11.553%	$174.9932	$174.99	$175.00	$175.00
7 purchase totals =	$650.83		$718.5620	$718.56	$718.55	$718.60