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	$168.57	9.451%	$184.5016	$184.50	$184.50	$184.50
Purchase #2	$35.77	4.844%	$37.5027	$37.50	$37.50	$37.50
Purchase #3	$119.61	13.262%	$135.4727	$135.47	$135.45	$135.50
Purchase #4	$177.94	8.153%	$192.4474	$192.45	$192.45	$192.40
Purchase #5	$114.75	4.413%	$119.8139	$119.81	$119.80	$119.80
Purchase #6	$58.91	9.516%	$64.5159	$64.52	$64.50	$64.50
Purchase #7	$48.47	8.258%	$52.4727	$52.47	$52.45	$52.50
7 purchase totals =	$724.02		$786.7269	$786.72	$786.65	$786.70