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	$234.60	9.300%	$256.4178	$256.42	$256.40	$256.40
Purchase #2	$13.57	9.445%	$14.8517	$14.85	$14.85	$14.90
Purchase #3	$48.85	13.172%	$55.2845	$55.28	$55.30	$55.30
Purchase #4	$42.83	8.518%	$46.4783	$46.48	$46.50	$46.50
Purchase #5	$49.74	13.858%	$56.633	$56.63	$56.65	$56.60
Purchase #6	$63.87	7.144%	$68.4329	$68.43	$68.45	$68.40
Purchase #7	$166.78	10.731%	$184.6772	$184.68	$184.70	$184.70
7 purchase totals =	$620.24		$682.7754	$682.77	$682.85	$682.80