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	$103.61	7.192%	$111.0616	$111.06	$111.05	$111.10
Purchase #2	$137.83	8.439%	$149.4615	$149.46	$149.45	$149.50
Purchase #3	$68.37	9.119%	$74.6047	$74.60	$74.60	$74.60
Purchase #4	$238.42	7.620%	$256.5876	$256.59	$256.60	$256.60
Purchase #5	$62.77	3.661%	$65.068	$65.07	$65.05	$65.10
Purchase #6	$66.82	3.121%	$68.9055	$68.91	$68.90	$68.90
Purchase #7	$167.31	13.822%	$190.4356	$190.44	$190.45	$190.40
7 purchase totals =	$845.13		$916.1245	$916.13	$916.10	$916.20