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	$107.41	3.671%	$111.353	$111.35	$111.35	$111.40
Purchase #2	$127.68	11.153%	$141.9202	$141.92	$141.90	$141.90
Purchase #3	$118.72	3.831%	$123.2682	$123.27	$123.25	$123.30
Purchase #4	$181.76	6.700%	$193.9379	$193.94	$193.95	$193.90
Purchase #5	$34.45	8.710%	$37.4506	$37.45	$37.45	$37.50
Purchase #6	$38.28	9.440%	$41.8936	$41.89	$41.90	$41.90
Purchase #7	$21.55	9.418%	$23.5796	$23.58	$23.60	$23.60
7 purchase totals =	$629.85		$673.4031	$673.40	$673.40	$673.50