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	$179.33	7.582%	$192.9268	$192.93	$192.95	$192.90
Purchase #2	$51.46	12.131%	$57.7026	$57.70	$57.70	$57.70
Purchase #3	$143.67	5.212%	$151.1581	$151.16	$151.15	$151.20
Purchase #4	$48.25	12.571%	$54.3155	$54.32	$54.30	$54.30
Purchase #5	$54.38	4.473%	$56.8124	$56.81	$56.80	$56.80
Purchase #6	$80.66	3.436%	$83.4315	$83.43	$83.45	$83.40
Purchase #7	$160.76	11.478%	$179.212	$179.21	$179.20	$179.20
7 purchase totals =	$718.51		$775.5589	$775.56	$775.55	$775.50