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	$236.40	10.210%	$260.5364	$260.54	$260.55	$260.50
Purchase #2	$10.34	4.730%	$10.8291	$10.83	$10.85	$10.80
Purchase #3	$151.64	10.397%	$167.406	$167.41	$167.40	$167.40
Purchase #4	$214.45	6.291%	$227.941	$227.94	$227.95	$227.90
Purchase #5	$188.40	3.431%	$194.864	$194.86	$194.85	$194.90
Purchase #6	$166.63	6.847%	$178.0392	$178.04	$178.05	$178.00
Purchase #7	$231.37	12.703%	$260.7609	$260.76	$260.75	$260.80
7 purchase totals =	$1,199.23		$1,300.3766	$1,300.38	$1,300.40	$1,300.30