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	$10.97	5.633%	$11.5879	$11.59	$11.60	$11.60
Purchase #2	$127.67	13.579%	$145.0063	$145.01	$145.00	$145.00
Purchase #3	$157.84	9.725%	$173.1899	$173.19	$173.20	$173.20
Purchase #4	$102.90	7.403%	$110.5177	$110.52	$110.50	$110.50
Purchase #5	$184.56	11.457%	$205.705	$205.71	$205.70	$205.70
Purchase #6	$151.48	11.220%	$168.4761	$168.48	$168.50	$168.50
Purchase #7	$247.40	11.271%	$275.2845	$275.28	$275.30	$275.30
7 purchase totals =	$982.82		$1,089.7674	$1,089.78	$1,089.80	$1,089.80