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	$227.38	11.648%	$253.8652	$253.87	$253.85	$253.90
Purchase #2	$42.68	4.587%	$44.6377	$44.64	$44.65	$44.60
Purchase #3	$112.93	10.769%	$125.0914	$125.09	$125.10	$125.10
Purchase #4	$239.38	8.518%	$259.7704	$259.77	$259.75	$259.80
Purchase #5	$48.53	11.795%	$54.2541	$54.25	$54.25	$54.30
Purchase #6	$118.37	7.523%	$127.275	$127.28	$127.30	$127.30
Purchase #7	$246.92	4.693%	$258.508	$258.51	$258.50	$258.50
7 purchase totals =	$1,036.19		$1,123.4018	$1,123.41	$1,123.40	$1,123.50