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	$247.67	3.823%	$257.1384	$257.14	$257.15	$257.10
Purchase #2	$228.80	4.262%	$238.5515	$238.55	$238.55	$238.60
Purchase #3	$180.65	3.103%	$186.2556	$186.26	$186.25	$186.30
Purchase #4	$216.26	5.220%	$227.5488	$227.55	$227.55	$227.50
Purchase #5	$46.25	12.603%	$52.0789	$52.08	$52.10	$52.10
Purchase #6	$40.63	13.823%	$46.2463	$46.25	$46.25	$46.20
Purchase #7	$101.46	9.549%	$111.1484	$111.15	$111.15	$111.10
7 purchase totals =	$1,061.72		$1,118.9679	$1,118.98	$1,119.00	$1,118.90