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	$79.29	7.779%	$85.458	$85.46	$85.45	$85.50
Purchase #2	$27.76	10.255%	$30.6068	$30.61	$30.60	$30.60
Purchase #3	$163.37	13.438%	$185.3237	$185.32	$185.30	$185.30
Purchase #4	$32.70	9.125%	$35.6839	$35.68	$35.70	$35.70
Purchase #5	$148.39	8.746%	$161.3682	$161.37	$161.35	$161.40
Purchase #6	$83.54	6.725%	$89.1581	$89.16	$89.15	$89.20
Purchase #7	$188.77	5.126%	$198.4464	$198.45	$198.45	$198.40
7 purchase totals =	$723.82		$786.0451	$786.05	$786.00	$786.10