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	$39.93	13.626%	$45.3709	$45.37	$45.35	$45.40
Purchase #2	$114.55	13.860%	$130.4266	$130.43	$130.45	$130.40
Purchase #3	$179.71	13.848%	$204.5962	$204.60	$204.60	$204.60
Purchase #4	$244.92	6.193%	$260.0879	$260.09	$260.10	$260.10
Purchase #5	$38.57	9.647%	$42.2908	$42.29	$42.30	$42.30
Purchase #6	$44.27	4.643%	$46.3255	$46.33	$46.35	$46.30
Purchase #7	$34.57	12.512%	$38.8954	$38.90	$38.90	$38.90
7 purchase totals =	$696.52		$767.9933	$768.01	$768.05	$768.00