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	$23.47	6.578%	$25.0139	$25.01	$25.00	$25.00
Purchase #2	$14.28	3.410%	$14.7669	$14.77	$14.75	$14.80
Purchase #3	$57.45	13.766%	$65.3586	$65.36	$65.35	$65.40
Purchase #4	$59.31	11.295%	$66.0091	$66.01	$66.00	$66.00
Purchase #5	$76.75	11.340%	$85.4535	$85.45	$85.45	$85.50
Purchase #6	$57.72	3.509%	$59.7454	$59.75	$59.75	$59.70
Purchase #7	$234.54	6.696%	$250.2448	$250.24	$250.25	$250.20
7 purchase totals =	$523.52		$566.5922	$566.59	$566.55	$566.60