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	$190.74	13.620%	$216.7188	$216.72	$216.70	$216.70
Purchase #2	$66.72	6.136%	$70.8139	$70.81	$70.80	$70.80
Purchase #3	$215.75	10.300%	$237.9723	$237.97	$237.95	$238.00
Purchase #4	$136.80	6.438%	$145.6072	$145.61	$145.60	$145.60
Purchase #5	$70.54	3.377%	$72.9221	$72.92	$72.90	$72.90
Purchase #6	$219.65	11.162%	$244.1673	$244.17	$244.15	$244.20
Purchase #7	$196.51	5.828%	$207.9626	$207.96	$207.95	$208.00
7 purchase totals =	$1,096.71		$1,196.1642	$1,196.16	$1,196.05	$1,196.20