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	$189.42	8.698%	$205.8958	$205.90	$205.90	$205.90
Purchase #2	$120.40	11.177%	$133.8571	$133.86	$133.85	$133.90
Purchase #3	$74.45	5.200%	$78.3214	$78.32	$78.30	$78.30
Purchase #4	$169.34	13.481%	$192.1687	$192.17	$192.15	$192.20
Purchase #5	$13.85	5.450%	$14.6048	$14.60	$14.60	$14.60
Purchase #6	$89.40	12.852%	$100.8897	$100.89	$100.90	$100.90
Purchase #7	$6.34	11.371%	$7.0609	$7.06	$7.05	$7.10
7 purchase totals =	$663.20		$732.7984	$732.80	$732.75	$732.90