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	$40.61	9.277%	$44.3774	$44.38	$44.40	$44.40
Purchase #2	$51.88	3.208%	$53.5443	$53.54	$53.55	$53.50
Purchase #3	$145.90	7.199%	$156.4033	$156.40	$156.40	$156.40
Purchase #4	$153.35	8.449%	$166.3065	$166.31	$166.30	$166.30
Purchase #5	$40.85	11.142%	$45.4015	$45.40	$45.40	$45.40
Purchase #6	$218.71	5.427%	$230.5794	$230.58	$230.60	$230.60
Purchase #7	$248.27	5.509%	$261.9472	$261.95	$261.95	$261.90
7 purchase totals =	$899.57		$958.5596	$958.56	$958.60	$958.50