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	$247.27	7.763%	$266.4656	$266.47	$266.45	$266.50
Purchase #2	$151.85	5.296%	$159.892	$159.89	$159.90	$159.90
Purchase #3	$117.43	8.744%	$127.6981	$127.70	$127.70	$127.70
Purchase #4	$91.42	7.112%	$97.9218	$97.92	$97.90	$97.90
Purchase #5	$66.50	8.368%	$72.0647	$72.06	$72.05	$72.10
Purchase #6	$90.68	12.240%	$101.7792	$101.78	$101.80	$101.80
Purchase #7	$21.89	5.360%	$23.0633	$23.06	$23.05	$23.10
7 purchase totals =	$787.04		$848.8847	$848.88	$848.85	$849.00