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	$102.57	9.167%	$111.9726	$111.97	$111.95	$112.00
Purchase #2	$70.29	10.162%	$77.4329	$77.43	$77.45	$77.40
Purchase #3	$184.75	6.213%	$196.2285	$196.23	$196.25	$196.20
Purchase #4	$143.39	13.491%	$162.7347	$162.73	$162.75	$162.70
Purchase #5	$169.77	9.278%	$185.5213	$185.52	$185.50	$185.50
Purchase #6	$135.74	4.561%	$141.9311	$141.93	$141.95	$141.90
Purchase #7	$56.73	11.496%	$63.2517	$63.25	$63.25	$63.30
7 purchase totals =	$863.24		$939.0728	$939.06	$939.10	$939.00