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	$62.62	3.209%	$64.6295	$64.63	$64.65	$64.60
Purchase #2	$127.35	13.552%	$144.6085	$144.61	$144.60	$144.60
Purchase #3	$153.49	3.528%	$158.9051	$158.91	$158.90	$158.90
Purchase #4	$58.52	13.253%	$66.2757	$66.28	$66.30	$66.30
Purchase #5	$42.92	7.319%	$46.0613	$46.06	$46.05	$46.10
Purchase #6	$60.59	8.156%	$65.5317	$65.53	$65.55	$65.50
Purchase #7	$80.43	3.223%	$83.0223	$83.02	$83.00	$83.00
7 purchase totals =	$585.92		$629.0341	$629.04	$629.05	$629.00