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	$22.98	12.419%	$25.8339	$25.83	$25.85	$25.80
Purchase #2	$68.47	6.342%	$72.8124	$72.81	$72.80	$72.80
Purchase #3	$226.55	10.282%	$249.8439	$249.84	$249.85	$249.80
Purchase #4	$63.40	4.350%	$66.1579	$66.16	$66.15	$66.20
Purchase #5	$247.86	13.200%	$280.5775	$280.58	$280.60	$280.60
Purchase #6	$158.73	5.686%	$167.7554	$167.76	$167.75	$167.80
Purchase #7	$222.38	4.795%	$233.0431	$233.04	$233.05	$233.00
7 purchase totals =	$1,010.37		$1,096.0241	$1,096.02	$1,096.05	$1,096.00