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	$200.84	11.105%	$223.1433	$223.14	$223.15	$223.10
Purchase #2	$132.46	10.566%	$146.4557	$146.46	$146.45	$146.50
Purchase #3	$11.73	10.812%	$12.9982	$13.00	$13.00	$13.00
Purchase #4	$75.26	9.829%	$82.6573	$82.66	$82.65	$82.70
Purchase #5	$224.33	6.455%	$238.8105	$238.81	$238.80	$238.80
Purchase #6	$18.43	13.462%	$20.911	$20.91	$20.90	$20.90
Purchase #7	$33.34	3.593%	$34.5379	$34.54	$34.55	$34.50
7 purchase totals =	$696.39		$759.5139	$759.52	$759.50	$759.50