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	$84.40	13.402%	$95.7113	$95.71	$95.70	$95.70
Purchase #2	$51.59	9.713%	$56.6009	$56.60	$56.60	$56.60
Purchase #3	$241.95	5.113%	$254.3209	$254.32	$254.30	$254.30
Purchase #4	$81.87	10.609%	$90.5556	$90.56	$90.55	$90.60
Purchase #5	$61.31	6.698%	$65.4165	$65.42	$65.40	$65.40
Purchase #6	$65.59	11.439%	$73.0928	$73.09	$73.10	$73.10
Purchase #7	$187.29	11.603%	$209.0213	$209.02	$209.00	$209.00
7 purchase totals =	$774.00		$844.7193	$844.72	$844.65	$844.70