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	$204.77	8.827%	$222.845	$222.85	$222.85	$222.80
Purchase #2	$44.86	10.264%	$49.4644	$49.46	$49.45	$49.50
Purchase #3	$213.69	4.577%	$223.4706	$223.47	$223.45	$223.50
Purchase #4	$73.77	8.218%	$79.8324	$79.83	$79.85	$79.80
Purchase #5	$48.76	9.772%	$53.5248	$53.52	$53.50	$53.50
Purchase #6	$185.76	10.502%	$205.2685	$205.27	$205.25	$205.30
Purchase #7	$136.67	13.175%	$154.6763	$154.68	$154.70	$154.70
7 purchase totals =	$908.28		$989.0820	$989.08	$989.05	$989.10