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	$209.83	3.446%	$217.0607	$217.06	$217.05	$217.10
Purchase #2	$176.98	7.407%	$190.0889	$190.09	$190.10	$190.10
Purchase #3	$100.89	9.418%	$110.3918	$110.39	$110.40	$110.40
Purchase #4	$155.40	10.433%	$171.6129	$171.61	$171.60	$171.60
Purchase #5	$240.81	4.661%	$252.0342	$252.03	$252.05	$252.00
Purchase #6	$153.54	5.399%	$161.8296	$161.83	$161.85	$161.80
Purchase #7	$146.27	4.204%	$152.4192	$152.42	$152.40	$152.40
7 purchase totals =	$1,183.72		$1,255.4373	$1,255.43	$1,255.45	$1,255.40