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	$52.92	5.508%	$55.8348	$55.83	$55.85	$55.80
Purchase #2	$30.45	13.725%	$34.6293	$34.63	$34.65	$34.60
Purchase #3	$51.38	8.294%	$55.6415	$55.64	$55.65	$55.60
Purchase #4	$99.28	6.111%	$105.347	$105.35	$105.35	$105.30
Purchase #5	$41.94	4.863%	$43.9795	$43.98	$44.00	$44.00
Purchase #6	$231.69	4.341%	$241.7477	$241.75	$241.75	$241.70
Purchase #7	$118.63	9.802%	$130.2581	$130.26	$130.25	$130.30
7 purchase totals =	$626.29		$667.4379	$667.44	$667.50	$667.30