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	$132.95	6.732%	$141.9002	$141.90	$141.90	$141.90
Purchase #2	$210.85	5.325%	$222.0778	$222.08	$222.10	$222.10
Purchase #3	$153.43	12.456%	$172.5412	$172.54	$172.55	$172.50
Purchase #4	$12.87	7.759%	$13.8686	$13.87	$13.85	$13.90
Purchase #5	$225.45	10.621%	$249.395	$249.40	$249.40	$249.40
Purchase #6	$210.78	13.271%	$238.7526	$238.75	$238.75	$238.80
Purchase #7	$191.60	7.478%	$205.9278	$205.93	$205.95	$205.90
7 purchase totals =	$1,137.93		$1,244.4632	$1,244.47	$1,244.50	$1,244.50