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	$126.42	5.103%	$132.8712	$132.87	$132.85	$132.90
Purchase #2	$153.78	11.516%	$171.4893	$171.49	$171.50	$171.50
Purchase #3	$134.51	5.188%	$141.4884	$141.49	$141.50	$141.50
Purchase #4	$16.28	7.521%	$17.5044	$17.50	$17.50	$17.50
Purchase #5	$78.37	4.276%	$81.7211	$81.72	$81.70	$81.70
Purchase #6	$49.75	9.374%	$54.4136	$54.41	$54.40	$54.40
Purchase #7	$75.72	9.183%	$82.6734	$82.67	$82.65	$82.70
7 purchase totals =	$634.83		$682.1614	$682.15	$682.10	$682.20