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	$37.26	11.138%	$41.41	$41.41	$41.40	$41.40
Purchase #2	$89.66	9.424%	$98.1096	$98.11	$98.10	$98.10
Purchase #3	$63.26	4.204%	$65.9195	$65.92	$65.90	$65.90
Purchase #4	$221.60	9.540%	$242.7406	$242.74	$242.75	$242.70
Purchase #5	$233.77	3.119%	$241.0613	$241.06	$241.05	$241.10
Purchase #6	$203.72	13.617%	$231.4606	$231.46	$231.45	$231.50
Purchase #7	$138.54	8.583%	$150.4309	$150.43	$150.45	$150.40
7 purchase totals =	$987.81		$1,071.1325	$1,071.13	$1,071.10	$1,071.10