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	$164.92	6.805%	$176.1428	$176.14	$176.15	$176.10
Purchase #2	$127.90	5.504%	$134.9396	$134.94	$134.95	$134.90
Purchase #3	$66.52	7.726%	$71.6593	$71.66	$71.65	$71.70
Purchase #4	$82.82	4.688%	$86.7026	$86.70	$86.70	$86.70
Purchase #5	$128.46	12.840%	$144.9543	$144.95	$144.95	$145.00
Purchase #6	$34.69	10.248%	$38.245	$38.25	$38.25	$38.20
Purchase #7	$7.27	4.382%	$7.5886	$7.59	$7.60	$7.60
7 purchase totals =	$612.58		$660.2322	$660.23	$660.25	$660.20