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	$99.37	13.581%	$112.8654	$112.87	$112.85	$112.90
Purchase #2	$51.85	7.127%	$55.5453	$55.55	$55.55	$55.50
Purchase #3	$218.59	3.426%	$226.0789	$226.08	$226.10	$226.10
Purchase #4	$214.36	9.363%	$234.4305	$234.43	$234.45	$234.40
Purchase #5	$89.43	10.147%	$98.5045	$98.50	$98.50	$98.50
Purchase #6	$74.62	8.141%	$80.6948	$80.69	$80.70	$80.70
Purchase #7	$214.60	10.656%	$237.4678	$237.47	$237.45	$237.50
7 purchase totals =	$962.82		$1,045.5872	$1,045.59	$1,045.60	$1,045.60