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	$85.38	8.737%	$92.8397	$92.84	$92.85	$92.80
Purchase #2	$89.75	7.622%	$96.5907	$96.59	$96.60	$96.60
Purchase #3	$196.88	4.406%	$205.5545	$205.55	$205.55	$205.60
Purchase #4	$226.81	5.253%	$238.7243	$238.72	$238.70	$238.70
Purchase #5	$9.58	9.316%	$10.4725	$10.47	$10.45	$10.50
Purchase #6	$123.50	13.471%	$140.1367	$140.14	$140.15	$140.10
Purchase #7	$208.88	12.670%	$235.3451	$235.35	$235.35	$235.30
7 purchase totals =	$940.78		$1,019.6635	$1,019.66	$1,019.65	$1,019.60