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	$153.27	7.429%	$164.6564	$164.66	$164.65	$164.70
Purchase #2	$148.45	3.704%	$153.9486	$153.95	$153.95	$153.90
Purchase #3	$19.93	6.433%	$21.2121	$21.21	$21.20	$21.20
Purchase #4	$76.90	10.394%	$84.893	$84.89	$84.90	$84.90
Purchase #5	$163.53	10.154%	$180.1348	$180.13	$180.15	$180.10
Purchase #6	$127.62	13.274%	$144.5603	$144.56	$144.55	$144.60
Purchase #7	$216.70	5.597%	$228.8287	$228.83	$228.85	$228.80
7 purchase totals =	$906.40		$978.2339	$978.23	$978.25	$978.20