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	$241.75	6.279%	$256.9295	$256.93	$256.95	$256.90
Purchase #2	$160.80	4.798%	$168.5152	$168.52	$168.50	$168.50
Purchase #3	$99.57	3.860%	$103.4134	$103.41	$103.40	$103.40
Purchase #4	$164.79	4.409%	$172.0556	$172.06	$172.05	$172.10
Purchase #5	$26.46	13.622%	$30.0644	$30.06	$30.05	$30.10
Purchase #6	$77.80	7.287%	$83.4693	$83.47	$83.45	$83.50
Purchase #7	$122.49	3.107%	$126.2958	$126.30	$126.30	$126.30
7 purchase totals =	$893.66		$940.7432	$940.75	$940.70	$940.80