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	$192.66	8.145%	$208.3522	$208.35	$208.35	$208.40
Purchase #2	$107.72	5.342%	$113.4744	$113.47	$113.45	$113.50
Purchase #3	$176.93	5.281%	$186.2737	$186.27	$186.25	$186.30
Purchase #4	$37.94	6.724%	$40.4911	$40.49	$40.50	$40.50
Purchase #5	$141.62	11.834%	$158.3793	$158.38	$158.40	$158.40
Purchase #6	$191.71	3.848%	$199.087	$199.09	$199.10	$199.10
Purchase #7	$32.82	13.687%	$37.3121	$37.31	$37.30	$37.30
7 purchase totals =	$881.40		$943.3698	$943.36	$943.35	$943.50