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	$151.29	3.376%	$156.3976	$156.40	$156.40	$156.40
Purchase #2	$159.57	4.104%	$166.1188	$166.12	$166.10	$166.10
Purchase #3	$207.47	5.532%	$218.9472	$218.95	$218.95	$218.90
Purchase #4	$107.53	4.718%	$112.6033	$112.60	$112.60	$112.60
Purchase #5	$111.26	6.463%	$118.4507	$118.45	$118.45	$118.50
Purchase #6	$49.54	6.595%	$52.8072	$52.81	$52.80	$52.80
Purchase #7	$229.45	4.767%	$240.3879	$240.39	$240.40	$240.40
7 purchase totals =	$1,016.11		$1,065.7127	$1,065.72	$1,065.70	$1,065.70