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	$43.84	4.585%	$45.8501	$45.85	$45.85	$45.90
Purchase #2	$48.74	5.456%	$51.3993	$51.40	$51.40	$51.40
Purchase #3	$170.78	7.641%	$183.8293	$183.83	$183.85	$183.80
Purchase #4	$62.62	5.231%	$65.8957	$65.90	$65.90	$65.90
Purchase #5	$238.36	5.828%	$252.2516	$252.25	$252.25	$252.30
Purchase #6	$77.41	12.205%	$86.8579	$86.86	$86.85	$86.90
Purchase #7	$214.89	4.481%	$224.5192	$224.52	$224.50	$224.50
7 purchase totals =	$856.64		$910.6031	$910.61	$910.60	$910.70