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	$39.71	9.821%	$43.6099	$43.61	$43.60	$43.60
Purchase #2	$161.31	7.496%	$173.4018	$173.40	$173.40	$173.40
Purchase #3	$44.59	9.140%	$48.6655	$48.67	$48.65	$48.70
Purchase #4	$64.74	3.315%	$66.8861	$66.89	$66.90	$66.90
Purchase #5	$40.80	13.739%	$46.4055	$46.41	$46.40	$46.40
Purchase #6	$80.68	13.115%	$91.2612	$91.26	$91.25	$91.30
Purchase #7	$47.98	9.141%	$52.3659	$52.37	$52.35	$52.40
7 purchase totals =	$479.81		$522.5959	$522.61	$522.55	$522.70