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	$112.65	13.189%	$127.5074	$127.51	$127.50	$127.50
Purchase #2	$11.36	5.473%	$11.9817	$11.98	$12.00	$12.00
Purchase #3	$111.64	6.233%	$118.5985	$118.60	$118.60	$118.60
Purchase #4	$157.92	13.854%	$179.7982	$179.80	$179.80	$179.80
Purchase #5	$218.80	11.363%	$243.6622	$243.66	$243.65	$243.70
Purchase #6	$119.83	3.851%	$124.4447	$124.44	$124.45	$124.40
Purchase #7	$36.29	10.733%	$40.185	$40.19	$40.20	$40.20
7 purchase totals =	$768.49		$846.1777	$846.18	$846.20	$846.20