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	$133.66	7.110%	$143.1632	$143.16	$143.15	$143.20
Purchase #2	$44.88	4.368%	$46.8404	$46.84	$46.85	$46.80
Purchase #3	$77.91	9.868%	$85.5982	$85.60	$85.60	$85.60
Purchase #4	$188.85	10.194%	$208.1014	$208.10	$208.10	$208.10
Purchase #5	$217.33	3.430%	$224.7844	$224.78	$224.80	$224.80
Purchase #6	$170.60	5.748%	$180.4061	$180.41	$180.40	$180.40
Purchase #7	$136.47	5.762%	$144.3334	$144.33	$144.35	$144.30
7 purchase totals =	$969.70		$1,033.2271	$1,033.22	$1,033.25	$1,033.20