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	$151.37	11.414%	$168.6474	$168.65	$168.65	$168.60
Purchase #2	$73.34	6.522%	$78.1232	$78.12	$78.10	$78.10
Purchase #3	$22.97	11.218%	$25.5468	$25.55	$25.55	$25.50
Purchase #4	$162.32	8.839%	$176.6675	$176.67	$176.65	$176.70
Purchase #5	$37.40	7.155%	$40.076	$40.08	$40.10	$40.10
Purchase #6	$66.51	6.451%	$70.8006	$70.80	$70.80	$70.80
Purchase #7	$24.59	5.549%	$25.9545	$25.95	$25.95	$26.00
7 purchase totals =	$538.50		$585.8160	$585.82	$585.80	$585.80