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	$127.28	8.463%	$138.0517	$138.05	$138.05	$138.10
Purchase #2	$22.44	10.808%	$24.8653	$24.87	$24.85	$24.90
Purchase #3	$11.51	7.324%	$12.353	$12.35	$12.35	$12.40
Purchase #4	$145.93	6.105%	$154.839	$154.84	$154.85	$154.80
Purchase #5	$11.59	5.707%	$12.2514	$12.25	$12.25	$12.30
Purchase #6	$56.47	5.425%	$59.5335	$59.53	$59.55	$59.50
Purchase #7	$197.38	12.208%	$221.4762	$221.48	$221.50	$221.50
7 purchase totals =	$572.60		$623.3701	$623.37	$623.40	$623.50