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	$100.57	12.109%	$112.748	$112.75	$112.75	$112.70
Purchase #2	$233.80	6.697%	$249.4576	$249.46	$249.45	$249.50
Purchase #3	$153.54	13.177%	$173.772	$173.77	$173.75	$173.80
Purchase #4	$242.31	5.586%	$255.8454	$255.85	$255.85	$255.80
Purchase #5	$9.26	13.496%	$10.5097	$10.51	$10.50	$10.50
Purchase #6	$50.86	9.328%	$55.6042	$55.60	$55.60	$55.60
Purchase #7	$142.96	7.274%	$153.3589	$153.36	$153.35	$153.40
7 purchase totals =	$933.30		$1,011.2958	$1,011.30	$1,011.25	$1,011.30