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	$167.41	13.775%	$190.4707	$190.47	$190.45	$190.50
Purchase #2	$116.83	10.733%	$129.3694	$129.37	$129.35	$129.40
Purchase #3	$168.32	13.743%	$191.4522	$191.45	$191.45	$191.50
Purchase #4	$139.77	8.763%	$152.018	$152.02	$152.00	$152.00
Purchase #5	$105.77	8.472%	$114.7308	$114.73	$114.75	$114.70
Purchase #6	$94.30	5.868%	$99.8335	$99.83	$99.85	$99.80
Purchase #7	$68.82	12.733%	$77.5829	$77.58	$77.60	$77.60
7 purchase totals =	$861.22		$955.4575	$955.45	$955.45	$955.50