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	$153.38	9.481%	$167.922	$167.92	$167.90	$167.90
Purchase #2	$116.69	6.262%	$123.9971	$124.00	$124.00	$124.00
Purchase #3	$102.92	8.668%	$111.8411	$111.84	$111.85	$111.80
Purchase #4	$216.59	10.172%	$238.6215	$238.62	$238.60	$238.60
Purchase #5	$100.36	11.441%	$111.8422	$111.84	$111.85	$111.80
Purchase #6	$73.77	3.241%	$76.1609	$76.16	$76.15	$76.20
Purchase #7	$237.92	7.734%	$256.3207	$256.32	$256.30	$256.30
7 purchase totals =	$1,001.63		$1,086.7055	$1,086.70	$1,086.65	$1,086.60