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	$158.41	5.691%	$167.4251	$167.43	$167.45	$167.40
Purchase #2	$144.29	5.262%	$151.8825	$151.88	$151.90	$151.90
Purchase #3	$246.79	13.297%	$279.6057	$279.61	$279.60	$279.60
Purchase #4	$63.40	10.778%	$70.2333	$70.23	$70.25	$70.20
Purchase #5	$186.99	12.513%	$210.3881	$210.39	$210.40	$210.40
Purchase #6	$136.81	12.763%	$154.2711	$154.27	$154.25	$154.30
Purchase #7	$92.46	10.788%	$102.4346	$102.43	$102.45	$102.40
7 purchase totals =	$1,029.15		$1,136.2404	$1,136.24	$1,136.30	$1,136.20