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	$116.47	9.510%	$127.5463	$127.55	$127.55	$127.50
Purchase #2	$34.52	7.429%	$37.0845	$37.08	$37.10	$37.10
Purchase #3	$192.64	3.329%	$199.053	$199.05	$199.05	$199.10
Purchase #4	$240.59	9.236%	$262.8109	$262.81	$262.80	$262.80
Purchase #5	$219.32	12.871%	$247.5487	$247.55	$247.55	$247.50
Purchase #6	$108.52	8.757%	$118.0231	$118.02	$118.00	$118.00
Purchase #7	$167.87	3.732%	$174.1349	$174.13	$174.15	$174.10
7 purchase totals =	$1,079.93		$1,166.2014	$1,166.19	$1,166.20	$1,166.10