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	$10.60	8.733%	$11.5257	$11.53	$11.55	$11.50
Purchase #2	$68.27	5.440%	$71.9839	$71.98	$72.00	$72.00
Purchase #3	$167.37	13.635%	$190.1909	$190.19	$190.20	$190.20
Purchase #4	$237.92	13.405%	$269.8132	$269.81	$269.80	$269.80
Purchase #5	$233.61	6.863%	$249.6427	$249.64	$249.65	$249.60
Purchase #6	$72.81	8.157%	$78.7491	$78.75	$78.75	$78.70
Purchase #7	$205.89	10.664%	$227.8461	$227.85	$227.85	$227.80
7 purchase totals =	$996.47		$1,099.7516	$1,099.75	$1,099.80	$1,099.60