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	$183.68	9.303%	$200.7678	$200.77	$200.75	$200.80
Purchase #2	$33.42	7.373%	$35.8841	$35.88	$35.90	$35.90
Purchase #3	$144.81	6.198%	$153.7853	$153.79	$153.80	$153.80
Purchase #4	$105.28	8.845%	$114.592	$114.59	$114.60	$114.60
Purchase #5	$181.30	8.539%	$196.7812	$196.78	$196.80	$196.80
Purchase #6	$41.85	6.678%	$44.6447	$44.64	$44.65	$44.60
Purchase #7	$152.32	7.863%	$164.2969	$164.30	$164.30	$164.30
7 purchase totals =	$842.66		$910.7520	$910.75	$910.80	$910.80