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	$207.87	9.607%	$227.8401	$227.84	$227.85	$227.80
Purchase #2	$98.32	6.566%	$104.7757	$104.78	$104.80	$104.80
Purchase #3	$32.46	10.387%	$35.8316	$35.83	$35.85	$35.80
Purchase #4	$39.31	5.304%	$41.395	$41.40	$41.40	$41.40
Purchase #5	$49.78	8.349%	$53.9361	$53.94	$53.95	$53.90
Purchase #6	$138.85	11.156%	$154.3401	$154.34	$154.35	$154.30
Purchase #7	$107.98	3.235%	$111.4732	$111.47	$111.45	$111.50
7 purchase totals =	$674.57		$729.5918	$729.60	$729.65	$729.50