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	$193.98	6.467%	$206.5247	$206.52	$206.50	$206.50
Purchase #2	$38.42	5.725%	$40.6195	$40.62	$40.60	$40.60
Purchase #3	$117.64	12.277%	$132.0827	$132.08	$132.10	$132.10
Purchase #4	$194.25	10.181%	$214.0266	$214.03	$214.05	$214.00
Purchase #5	$39.75	6.844%	$42.4705	$42.47	$42.45	$42.50
Purchase #6	$99.65	3.873%	$103.5094	$103.51	$103.50	$103.50
Purchase #7	$102.86	11.354%	$114.5387	$114.54	$114.55	$114.50
7 purchase totals =	$786.55		$853.7721	$853.77	$853.75	$853.70