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	$38.26	13.231%	$43.3222	$43.32	$43.30	$43.30
Purchase #2	$50.77	4.174%	$52.8891	$52.89	$52.90	$52.90
Purchase #3	$39.66	3.131%	$40.9018	$40.90	$40.90	$40.90
Purchase #4	$178.37	8.141%	$192.8911	$192.89	$192.90	$192.90
Purchase #5	$48.80	9.332%	$53.354	$53.35	$53.35	$53.40
Purchase #6	$214.85	7.248%	$230.4223	$230.42	$230.40	$230.40
Purchase #7	$41.47	5.699%	$43.8334	$43.83	$43.85	$43.80
7 purchase totals =	$612.18		$657.6139	$657.60	$657.60	$657.60