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	$115.78	9.154%	$126.3785	$126.38	$126.40	$126.40
Purchase #2	$132.93	8.416%	$144.1174	$144.12	$144.10	$144.10
Purchase #3	$39.85	13.747%	$45.3282	$45.33	$45.35	$45.30
Purchase #4	$233.50	13.530%	$265.0926	$265.09	$265.10	$265.10
Purchase #5	$119.59	6.302%	$127.1266	$127.13	$127.15	$127.10
Purchase #6	$229.89	3.860%	$238.7638	$238.76	$238.75	$238.80
Purchase #7	$30.68	4.416%	$32.0348	$32.03	$32.05	$32.00
7 purchase totals =	$902.22		$978.8419	$978.84	$978.90	$978.80