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	$53.88	13.323%	$61.0584	$61.06	$61.05	$61.10
Purchase #2	$95.99	13.389%	$108.8421	$108.84	$108.85	$108.80
Purchase #3	$93.80	12.249%	$105.2896	$105.29	$105.30	$105.30
Purchase #4	$80.58	9.296%	$88.0707	$88.07	$88.05	$88.10
Purchase #5	$56.39	13.249%	$63.8611	$63.86	$63.85	$63.90
Purchase #6	$215.25	11.772%	$240.5892	$240.59	$240.60	$240.60
Purchase #7	$177.96	10.684%	$196.9732	$196.97	$196.95	$197.00
7 purchase totals =	$773.85		$864.6843	$864.68	$864.65	$864.80