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	$74.49	5.307%	$78.4432	$78.44	$78.45	$78.40
Purchase #2	$132.34	5.379%	$139.4586	$139.46	$139.45	$139.50
Purchase #3	$195.42	13.382%	$221.5711	$221.57	$221.55	$221.60
Purchase #4	$111.76	10.592%	$123.5976	$123.60	$123.60	$123.60
Purchase #5	$58.85	13.366%	$66.7159	$66.72	$66.70	$66.70
Purchase #6	$198.25	7.113%	$212.3515	$212.35	$212.35	$212.40
Purchase #7	$230.45	6.368%	$245.1251	$245.13	$245.15	$245.10
7 purchase totals =	$1,001.56		$1,087.2630	$1,087.27	$1,087.25	$1,087.30