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	$165.44	5.446%	$174.4499	$174.45	$174.45	$174.40
Purchase #2	$177.98	4.172%	$185.4053	$185.41	$185.40	$185.40
Purchase #3	$177.62	5.210%	$186.874	$186.87	$186.85	$186.90
Purchase #4	$17.36	4.407%	$18.1251	$18.13	$18.15	$18.10
Purchase #5	$99.71	6.833%	$106.5232	$106.52	$106.50	$106.50
Purchase #6	$63.38	4.223%	$66.0565	$66.06	$66.05	$66.10
Purchase #7	$104.41	13.592%	$118.6014	$118.60	$118.60	$118.60
7 purchase totals =	$805.90		$856.0354	$856.04	$856.00	$856.00