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	$51.37	6.789%	$54.8575	$54.86	$54.85	$54.90
Purchase #2	$79.60	13.155%	$90.0714	$90.07	$90.05	$90.10
Purchase #3	$126.41	12.155%	$141.7751	$141.78	$141.80	$141.80
Purchase #4	$230.80	11.378%	$257.0604	$257.06	$257.05	$257.10
Purchase #5	$228.79	11.852%	$255.9062	$255.91	$255.90	$255.90
Purchase #6	$43.43	5.404%	$45.777	$45.78	$45.80	$45.80
Purchase #7	$183.60	3.824%	$190.6209	$190.62	$190.60	$190.60
7 purchase totals =	$944.00		$1,036.0685	$1,036.08	$1,036.05	$1,036.20