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	$133.64	9.635%	$146.5162	$146.52	$146.50	$146.50
Purchase #2	$45.29	3.480%	$46.8661	$46.87	$46.85	$46.90
Purchase #3	$49.80	10.339%	$54.9488	$54.95	$54.95	$54.90
Purchase #4	$86.32	10.651%	$95.5139	$95.51	$95.50	$95.50
Purchase #5	$10.84	12.580%	$12.2037	$12.20	$12.20	$12.20
Purchase #6	$19.79	3.140%	$20.4114	$20.41	$20.40	$20.40
Purchase #7	$136.95	8.133%	$148.0881	$148.09	$148.10	$148.10
7 purchase totals =	$482.63		$524.5482	$524.55	$524.50	$524.50