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	$127.39	12.103%	$142.808	$142.81	$142.80	$142.80
Purchase #2	$12.51	5.312%	$13.1745	$13.17	$13.15	$13.20
Purchase #3	$130.47	11.138%	$145.0017	$145.00	$145.00	$145.00
Purchase #4	$122.71	11.768%	$137.1505	$137.15	$137.15	$137.20
Purchase #5	$250.59	13.440%	$284.2693	$284.27	$284.25	$284.30
Purchase #6	$192.49	6.295%	$204.6072	$204.61	$204.60	$204.60
Purchase #7	$6.48	6.194%	$6.8814	$6.88	$6.90	$6.90
7 purchase totals =	$842.64		$933.8926	$933.89	$933.85	$934.00