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	$62.97	4.104%	$65.5543	$65.55	$65.55	$65.60
Purchase #2	$47.72	10.628%	$52.7917	$52.79	$52.80	$52.80
Purchase #3	$10.98	9.506%	$12.0238	$12.02	$12.00	$12.00
Purchase #4	$176.71	9.166%	$192.9072	$192.91	$192.90	$192.90
Purchase #5	$249.77	10.774%	$276.6802	$276.68	$276.70	$276.70
Purchase #6	$92.94	13.607%	$105.5863	$105.59	$105.60	$105.60
Purchase #7	$85.93	5.728%	$90.8521	$90.85	$90.85	$90.90
7 purchase totals =	$727.02		$796.3956	$796.39	$796.40	$796.50