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	$208.57	9.307%	$227.9816	$227.98	$228.00	$228.00
Purchase #2	$71.68	6.792%	$76.5485	$76.55	$76.55	$76.50
Purchase #3	$164.86	11.703%	$184.1536	$184.15	$184.15	$184.20
Purchase #4	$170.59	3.521%	$176.5965	$176.60	$176.60	$176.60
Purchase #5	$233.57	5.251%	$245.8348	$245.83	$245.85	$245.80
Purchase #6	$90.72	10.693%	$100.4207	$100.42	$100.40	$100.40
Purchase #7	$136.51	3.343%	$141.0735	$141.07	$141.05	$141.10
7 purchase totals =	$1,076.50		$1,152.6092	$1,152.60	$1,152.60	$1,152.60