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	$202.51	9.841%	$222.439	$222.44	$222.45	$222.40
Purchase #2	$61.42	3.491%	$63.5642	$63.56	$63.55	$63.60
Purchase #3	$208.60	6.632%	$222.4344	$222.43	$222.45	$222.40
Purchase #4	$100.50	5.287%	$105.8134	$105.81	$105.80	$105.80
Purchase #5	$194.91	10.192%	$214.7752	$214.78	$214.80	$214.80
Purchase #6	$51.70	3.164%	$53.3358	$53.34	$53.35	$53.30
Purchase #7	$64.95	6.353%	$69.0763	$69.08	$69.10	$69.10
7 purchase totals =	$884.59		$951.4383	$951.44	$951.50	$951.40