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	$92.91	13.678%	$105.6182	$105.62	$105.60	$105.60
Purchase #2	$8.73	8.768%	$9.4954	$9.50	$9.50	$9.50
Purchase #3	$185.85	5.534%	$196.1349	$196.13	$196.15	$196.10
Purchase #4	$112.38	6.369%	$119.5375	$119.54	$119.55	$119.50
Purchase #5	$14.83	10.319%	$16.3603	$16.36	$16.35	$16.40
Purchase #6	$72.26	8.488%	$78.3934	$78.39	$78.40	$78.40
Purchase #7	$48.97	7.147%	$52.4699	$52.47	$52.45	$52.50
7 purchase totals =	$535.93		$578.0096	$578.01	$578.00	$578.00