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	$245.46	5.517%	$259.002	$259.00	$259.00	$259.00
Purchase #2	$83.93	6.418%	$89.3166	$89.32	$89.30	$89.30
Purchase #3	$95.27	9.223%	$104.0568	$104.06	$104.05	$104.10
Purchase #4	$137.69	5.623%	$145.4323	$145.43	$145.45	$145.40
Purchase #5	$84.92	12.509%	$95.5426	$95.54	$95.55	$95.50
Purchase #6	$194.45	13.499%	$220.6988	$220.70	$220.70	$220.70
Purchase #7	$166.25	4.301%	$173.4004	$173.40	$173.40	$173.40
7 purchase totals =	$1,007.97		$1,087.4495	$1,087.45	$1,087.45	$1,087.40