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	$153.52	6.523%	$163.5341	$163.53	$163.55	$163.50
Purchase #2	$177.86	11.495%	$198.305	$198.31	$198.30	$198.30
Purchase #3	$127.38	3.128%	$131.3644	$131.36	$131.35	$131.40
Purchase #4	$130.32	9.527%	$142.7356	$142.74	$142.75	$142.70
Purchase #5	$37.36	13.210%	$42.2953	$42.30	$42.30	$42.30
Purchase #6	$208.77	6.562%	$222.4695	$222.47	$222.45	$222.50
Purchase #7	$66.30	5.246%	$69.7781	$69.78	$69.80	$69.80
7 purchase totals =	$901.51		$970.4820	$970.49	$970.50	$970.50