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	$84.43	7.462%	$90.7302	$90.73	$90.75	$90.70
Purchase #2	$13.81	11.751%	$15.4328	$15.43	$15.45	$15.40
Purchase #3	$162.50	11.664%	$181.454	$181.45	$181.45	$181.50
Purchase #4	$180.49	3.824%	$187.3919	$187.39	$187.40	$187.40
Purchase #5	$216.51	4.783%	$226.8657	$226.87	$226.85	$226.90
Purchase #6	$52.91	6.325%	$56.2566	$56.26	$56.25	$56.30
Purchase #7	$50.52	5.587%	$53.3426	$53.34	$53.35	$53.30
7 purchase totals =	$761.17		$811.4738	$811.47	$811.50	$811.50