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	$242.47	12.412%	$272.5654	$272.57	$272.55	$272.60
Purchase #2	$69.54	3.748%	$72.1464	$72.15	$72.15	$72.10
Purchase #3	$114.70	10.799%	$127.0865	$127.09	$127.10	$127.10
Purchase #4	$211.76	12.835%	$238.9394	$238.94	$238.95	$238.90
Purchase #5	$32.27	7.500%	$34.6903	$34.69	$34.70	$34.70
Purchase #6	$180.52	6.635%	$192.4975	$192.50	$192.50	$192.50
Purchase #7	$113.93	7.591%	$122.5784	$122.58	$122.60	$122.60
7 purchase totals =	$965.19		$1,060.5039	$1,060.52	$1,060.55	$1,060.50