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	$20.84	11.595%	$23.2564	$23.26	$23.25	$23.30
Purchase #2	$175.54	5.260%	$184.7734	$184.77	$184.75	$184.80
Purchase #3	$151.51	6.175%	$160.8657	$160.87	$160.85	$160.90
Purchase #4	$158.89	3.575%	$164.5703	$164.57	$164.55	$164.60
Purchase #5	$215.90	3.806%	$224.1172	$224.12	$224.10	$224.10
Purchase #6	$234.60	9.306%	$256.4319	$256.43	$256.45	$256.40
Purchase #7	$119.86	6.350%	$127.4711	$127.47	$127.45	$127.50
7 purchase totals =	$1,077.14		$1,141.4860	$1,141.49	$1,141.40	$1,141.60