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	$11.60	3.712%	$12.0306	$12.03	$12.05	$12.00
Purchase #2	$121.71	3.698%	$126.2108	$126.21	$126.20	$126.20
Purchase #3	$161.42	3.731%	$167.4426	$167.44	$167.45	$167.40
Purchase #4	$192.83	12.422%	$216.7833	$216.78	$216.80	$216.80
Purchase #5	$120.83	5.663%	$127.6726	$127.67	$127.65	$127.70
Purchase #6	$46.62	13.481%	$52.9048	$52.90	$52.90	$52.90
Purchase #7	$128.73	11.304%	$143.2816	$143.28	$143.30	$143.30
7 purchase totals =	$783.74		$846.3263	$846.31	$846.35	$846.30