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	$107.42	3.414%	$111.0873	$111.09	$111.10	$111.10
Purchase #2	$141.59	10.593%	$156.5886	$156.59	$156.60	$156.60
Purchase #3	$127.28	11.269%	$141.6232	$141.62	$141.60	$141.60
Purchase #4	$196.89	12.595%	$221.6883	$221.69	$221.70	$221.70
Purchase #5	$199.54	9.834%	$219.1628	$219.16	$219.15	$219.20
Purchase #6	$143.70	7.562%	$154.5666	$154.57	$154.55	$154.60
Purchase #7	$190.91	12.385%	$214.5542	$214.55	$214.55	$214.60
7 purchase totals =	$1,107.33		$1,219.2710	$1,219.27	$1,219.25	$1,219.40