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	$95.38	11.271%	$106.1303	$106.13	$106.15	$106.10
Purchase #2	$125.41	12.158%	$140.6573	$140.66	$140.65	$140.70
Purchase #3	$117.76	8.573%	$127.8556	$127.86	$127.85	$127.90
Purchase #4	$183.59	7.291%	$196.9755	$196.98	$197.00	$197.00
Purchase #5	$90.72	8.634%	$98.5528	$98.55	$98.55	$98.60
Purchase #6	$179.66	13.638%	$204.162	$204.16	$204.15	$204.20
Purchase #7	$109.41	13.579%	$124.2668	$124.27	$124.25	$124.30
7 purchase totals =	$901.93		$998.6003	$998.61	$998.60	$998.80