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	$64.44	12.792%	$72.6832	$72.68	$72.70	$72.70
Purchase #2	$240.56	6.783%	$256.8772	$256.88	$256.90	$256.90
Purchase #3	$191.65	8.140%	$207.2503	$207.25	$207.25	$207.30
Purchase #4	$94.60	9.462%	$103.5511	$103.55	$103.55	$103.60
Purchase #5	$159.46	5.464%	$168.1729	$168.17	$168.15	$168.20
Purchase #6	$116.53	9.411%	$127.4966	$127.50	$127.50	$127.50
Purchase #7	$202.27	11.761%	$226.059	$226.06	$226.05	$226.10
7 purchase totals =	$1,069.51		$1,162.0903	$1,162.09	$1,162.10	$1,162.30