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	$177.85	4.297%	$185.4922	$185.49	$185.50	$185.50
Purchase #2	$55.38	12.784%	$62.4598	$62.46	$62.45	$62.50
Purchase #3	$109.93	12.626%	$123.8098	$123.81	$123.80	$123.80
Purchase #4	$233.90	9.426%	$255.9474	$255.95	$255.95	$255.90
Purchase #5	$163.85	3.152%	$169.0146	$169.01	$169.00	$169.00
Purchase #6	$133.65	13.634%	$151.8718	$151.87	$151.85	$151.90
Purchase #7	$54.69	11.398%	$60.9236	$60.92	$60.90	$60.90
7 purchase totals =	$929.25		$1,009.5192	$1,009.51	$1,009.45	$1,009.50