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	$102.45	5.837%	$108.43	$108.43	$108.45	$108.40
Purchase #2	$98.78	12.848%	$111.4713	$111.47	$111.45	$111.50
Purchase #3	$62.46	4.678%	$65.3819	$65.38	$65.40	$65.40
Purchase #4	$176.84	4.769%	$185.2735	$185.27	$185.25	$185.30
Purchase #5	$15.41	12.696%	$17.3665	$17.37	$17.35	$17.40
Purchase #6	$95.39	10.749%	$105.6435	$105.64	$105.65	$105.60
Purchase #7	$132.49	6.631%	$141.2754	$141.28	$141.30	$141.30
7 purchase totals =	$683.82		$734.8421	$734.84	$734.85	$734.90