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	$144.46	9.676%	$158.4379	$158.44	$158.45	$158.40
Purchase #2	$136.49	4.138%	$142.138	$142.14	$142.15	$142.10
Purchase #3	$127.56	4.638%	$133.4762	$133.48	$133.50	$133.50
Purchase #4	$86.46	7.665%	$93.0872	$93.09	$93.10	$93.10
Purchase #5	$211.26	4.798%	$221.3963	$221.40	$221.40	$221.40
Purchase #6	$96.26	7.814%	$103.7818	$103.78	$103.80	$103.80
Purchase #7	$105.60	5.771%	$111.6942	$111.69	$111.70	$111.70
7 purchase totals =	$908.09		$964.0116	$964.02	$964.10	$964.00