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	$234.50	8.114%	$253.5273	$253.53	$253.55	$253.50
Purchase #2	$154.44	9.406%	$168.9666	$168.97	$168.95	$169.00
Purchase #3	$236.45	5.548%	$249.5682	$249.57	$249.55	$249.60
Purchase #4	$145.38	3.244%	$150.0961	$150.10	$150.10	$150.10
Purchase #5	$130.25	11.774%	$145.5856	$145.59	$145.60	$145.60
Purchase #6	$167.85	11.788%	$187.6362	$187.64	$187.65	$187.60
Purchase #7	$126.56	12.568%	$142.4661	$142.47	$142.45	$142.50
7 purchase totals =	$1,195.43		$1,297.8461	$1,297.87	$1,297.85	$1,297.90