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	$58.61	6.195%	$62.2409	$62.24	$62.25	$62.20
Purchase #2	$12.67	4.127%	$13.1929	$13.19	$13.20	$13.20
Purchase #3	$48.30	8.580%	$52.4441	$52.44	$52.45	$52.40
Purchase #4	$87.32	10.839%	$96.7846	$96.78	$96.80	$96.80
Purchase #5	$100.42	10.669%	$111.1338	$111.13	$111.15	$111.10
Purchase #6	$67.88	4.520%	$70.9482	$70.95	$70.95	$70.90
Purchase #7	$78.44	9.393%	$85.8079	$85.81	$85.80	$85.80
7 purchase totals =	$453.64		$492.5524	$492.54	$492.60	$492.40