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	$41.68	11.458%	$46.4557	$46.46	$46.45	$46.50
Purchase #2	$160.47	4.627%	$167.8949	$167.89	$167.90	$167.90
Purchase #3	$45.79	8.270%	$49.5768	$49.58	$49.60	$49.60
Purchase #4	$50.29	11.576%	$56.1116	$56.11	$56.10	$56.10
Purchase #5	$136.67	10.517%	$151.0436	$151.04	$151.05	$151.00
Purchase #6	$223.69	4.560%	$233.8903	$233.89	$233.90	$233.90
Purchase #7	$154.36	11.762%	$172.5158	$172.52	$172.50	$172.50
7 purchase totals =	$812.95		$877.4887	$877.49	$877.50	$877.50