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	$171.77	7.845%	$185.2454	$185.25	$185.25	$185.20
Purchase #2	$64.69	12.533%	$72.7976	$72.80	$72.80	$72.80
Purchase #3	$153.86	4.239%	$160.3821	$160.38	$160.40	$160.40
Purchase #4	$38.45	5.615%	$40.609	$40.61	$40.60	$40.60
Purchase #5	$64.62	3.312%	$66.7602	$66.76	$66.75	$66.80
Purchase #6	$83.89	6.245%	$89.1289	$89.13	$89.15	$89.10
Purchase #7	$103.71	8.279%	$112.2962	$112.30	$112.30	$112.30
7 purchase totals =	$680.99		$727.2194	$727.23	$727.25	$727.20