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	$219.86	9.540%	$240.8346	$240.83	$240.85	$240.80
Purchase #2	$77.42	10.429%	$85.4941	$85.49	$85.50	$85.50
Purchase #3	$121.69	9.798%	$133.6132	$133.61	$133.60	$133.60
Purchase #4	$12.85	8.192%	$13.9027	$13.90	$13.90	$13.90
Purchase #5	$94.90	4.460%	$99.1325	$99.13	$99.15	$99.10
Purchase #6	$211.86	3.342%	$218.9404	$218.94	$218.95	$218.90
Purchase #7	$239.78	5.289%	$252.462	$252.46	$252.45	$252.50
7 purchase totals =	$978.36		$1,044.3795	$1,044.36	$1,044.40	$1,044.30