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	$112.81	4.456%	$117.8368	$117.84	$117.85	$117.80
Purchase #2	$40.81	12.233%	$45.8023	$45.80	$45.80	$45.80
Purchase #3	$11.30	9.833%	$12.4111	$12.41	$12.40	$12.40
Purchase #4	$104.57	6.227%	$111.0816	$111.08	$111.10	$111.10
Purchase #5	$56.52	13.742%	$64.287	$64.29	$64.30	$64.30
Purchase #6	$163.90	12.188%	$183.8761	$183.88	$183.90	$183.90
Purchase #7	$29.31	11.310%	$32.625	$32.63	$32.65	$32.60
7 purchase totals =	$519.22		$567.9199	$567.93	$568.00	$567.90