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	$108.46	9.662%	$118.9394	$118.94	$118.95	$118.90
Purchase #2	$240.40	3.702%	$249.2996	$249.30	$249.30	$249.30
Purchase #3	$131.74	6.177%	$139.8776	$139.88	$139.90	$139.90
Purchase #4	$65.83	5.262%	$69.294	$69.29	$69.30	$69.30
Purchase #5	$12.89	6.562%	$13.7358	$13.74	$13.75	$13.70
Purchase #6	$139.40	12.491%	$156.8125	$156.81	$156.80	$156.80
Purchase #7	$108.60	13.388%	$123.1394	$123.14	$123.15	$123.10
7 purchase totals =	$807.32		$871.0983	$871.10	$871.15	$871.00