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	$9.43	11.769%	$10.5398	$10.54	$10.55	$10.50
Purchase #2	$223.27	11.747%	$249.4975	$249.50	$249.50	$249.50
Purchase #3	$196.52	9.346%	$214.8868	$214.89	$214.90	$214.90
Purchase #4	$50.66	8.668%	$55.0512	$55.05	$55.05	$55.10
Purchase #5	$147.39	13.694%	$167.5736	$167.57	$167.55	$167.60
Purchase #6	$162.76	4.174%	$169.5536	$169.55	$169.55	$169.60
Purchase #7	$56.85	8.866%	$61.8903	$61.89	$61.90	$61.90
7 purchase totals =	$846.88		$928.9928	$928.99	$929.00	$929.10