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	$133.27	11.733%	$148.9066	$148.91	$148.90	$148.90
Purchase #2	$27.41	9.585%	$30.0372	$30.04	$30.05	$30.00
Purchase #3	$75.43	11.161%	$83.8487	$83.85	$83.85	$83.80
Purchase #4	$186.54	12.294%	$209.4732	$209.47	$209.45	$209.50
Purchase #5	$51.83	4.492%	$54.1582	$54.16	$54.15	$54.20
Purchase #6	$116.81	9.856%	$128.3228	$128.32	$128.30	$128.30
Purchase #7	$118.72	11.237%	$132.0606	$132.06	$132.05	$132.10
7 purchase totals =	$710.01		$786.8073	$786.81	$786.75	$786.80