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	$227.65	9.605%	$249.5158	$249.52	$249.50	$249.50
Purchase #2	$40.60	10.561%	$44.8878	$44.89	$44.90	$44.90
Purchase #3	$24.29	11.431%	$27.0666	$27.07	$27.05	$27.10
Purchase #4	$179.46	9.639%	$196.7581	$196.76	$196.75	$196.80
Purchase #5	$250.67	11.505%	$279.5096	$279.51	$279.50	$279.50
Purchase #6	$41.29	5.454%	$43.542	$43.54	$43.55	$43.50
Purchase #7	$233.76	5.248%	$246.0277	$246.03	$246.05	$246.00
7 purchase totals =	$997.72		$1,087.3076	$1,087.32	$1,087.30	$1,087.30