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	$217.36	9.771%	$238.5982	$238.60	$238.60	$238.60
Purchase #2	$59.62	10.193%	$65.6971	$65.70	$65.70	$65.70
Purchase #3	$132.98	11.782%	$148.6477	$148.65	$148.65	$148.60
Purchase #4	$36.47	11.115%	$40.5236	$40.52	$40.50	$40.50
Purchase #5	$234.27	13.816%	$266.6367	$266.64	$266.65	$266.60
Purchase #6	$222.86	10.849%	$247.0381	$247.04	$247.05	$247.00
Purchase #7	$152.42	6.694%	$162.623	$162.62	$162.60	$162.60
7 purchase totals =	$1,055.98		$1,169.7644	$1,169.77	$1,169.75	$1,169.60