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	$154.94	6.176%	$164.5091	$164.51	$164.50	$164.50
Purchase #2	$11.96	5.522%	$12.6204	$12.62	$12.60	$12.60
Purchase #3	$46.75	5.375%	$49.2628	$49.26	$49.25	$49.30
Purchase #4	$196.69	8.505%	$213.4185	$213.42	$213.40	$213.40
Purchase #5	$148.80	10.509%	$164.4374	$164.44	$164.45	$164.40
Purchase #6	$138.72	9.373%	$151.7222	$151.72	$151.70	$151.70
Purchase #7	$131.94	9.184%	$144.0574	$144.06	$144.05	$144.10
7 purchase totals =	$829.80		$900.0278	$900.03	$899.95	$900.00