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	$80.63	13.454%	$91.478	$91.48	$91.50	$91.50
Purchase #2	$70.68	5.180%	$74.3412	$74.34	$74.35	$74.30
Purchase #3	$53.52	11.847%	$59.8605	$59.86	$59.85	$59.90
Purchase #4	$9.56	4.698%	$10.0091	$10.01	$10.00	$10.00
Purchase #5	$137.84	11.201%	$153.2795	$153.28	$153.30	$153.30
Purchase #6	$225.85	5.389%	$238.0211	$238.02	$238.00	$238.00
Purchase #7	$6.78	12.422%	$7.6222	$7.62	$7.60	$7.60
7 purchase totals =	$584.86		$634.6116	$634.61	$634.60	$634.60