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	$193.30	11.302%	$215.1468	$215.15	$215.15	$215.10
Purchase #2	$76.56	9.354%	$83.7214	$83.72	$83.70	$83.70
Purchase #3	$105.58	8.229%	$114.2682	$114.27	$114.25	$114.30
Purchase #4	$154.88	6.720%	$165.2879	$165.29	$165.30	$165.30
Purchase #5	$56.53	6.135%	$59.9981	$60.00	$60.00	$60.00
Purchase #6	$33.90	10.383%	$37.4198	$37.42	$37.40	$37.40
Purchase #7	$93.35	6.313%	$99.2432	$99.24	$99.25	$99.20
7 purchase totals =	$714.10		$775.0854	$775.09	$775.05	$775.00