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	$119.87	9.769%	$131.5801	$131.58	$131.60	$131.60
Purchase #2	$123.39	13.355%	$139.8687	$139.87	$139.85	$139.90
Purchase #3	$18.69	8.195%	$20.2216	$20.22	$20.20	$20.20
Purchase #4	$11.26	10.567%	$12.4498	$12.45	$12.45	$12.40
Purchase #5	$92.80	13.554%	$105.3781	$105.38	$105.40	$105.40
Purchase #6	$206.99	8.500%	$224.5842	$224.58	$224.60	$224.60
Purchase #7	$104.62	8.140%	$113.1361	$113.14	$113.15	$113.10
7 purchase totals =	$677.62		$747.2186	$747.22	$747.25	$747.20