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	$194.60	7.322%	$208.8486	$208.85	$208.85	$208.80
Purchase #2	$150.74	11.218%	$167.65	$167.65	$167.65	$167.70
Purchase #3	$13.72	5.182%	$14.431	$14.43	$14.45	$14.40
Purchase #4	$11.34	4.659%	$11.8683	$11.87	$11.85	$11.90
Purchase #5	$170.68	12.211%	$191.5217	$191.52	$191.50	$191.50
Purchase #6	$225.87	7.383%	$242.546	$242.55	$242.55	$242.50
Purchase #7	$127.96	3.116%	$131.9472	$131.95	$131.95	$131.90
7 purchase totals =	$894.91		$968.8128	$968.82	$968.80	$968.70