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	$49.25	8.184%	$53.2806	$53.28	$53.30	$53.30
Purchase #2	$117.97	13.128%	$133.4571	$133.46	$133.45	$133.50
Purchase #3	$35.97	12.836%	$40.5871	$40.59	$40.60	$40.60
Purchase #4	$88.48	8.307%	$95.83	$95.83	$95.85	$95.80
Purchase #5	$228.57	4.576%	$239.0294	$239.03	$239.05	$239.00
Purchase #6	$56.44	5.407%	$59.4917	$59.49	$59.50	$59.50
Purchase #7	$68.36	3.183%	$70.5359	$70.54	$70.55	$70.50
7 purchase totals =	$645.04		$692.2118	$692.22	$692.30	$692.20