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	$127.27	9.220%	$139.0043	$139.00	$139.00	$139.00
Purchase #2	$21.34	9.309%	$23.3265	$23.33	$23.35	$23.30
Purchase #3	$49.82	8.533%	$54.0711	$54.07	$54.05	$54.10
Purchase #4	$128.85	10.653%	$142.5764	$142.58	$142.60	$142.60
Purchase #5	$230.35	3.343%	$238.0506	$238.05	$238.05	$238.10
Purchase #6	$107.83	10.852%	$119.5317	$119.53	$119.55	$119.50
Purchase #7	$20.69	4.644%	$21.6508	$21.65	$21.65	$21.70
7 purchase totals =	$686.15		$738.2114	$738.21	$738.25	$738.30