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	$226.73	3.176%	$233.9309	$233.93	$233.95	$233.90
Purchase #2	$104.43	6.351%	$111.0623	$111.06	$111.05	$111.10
Purchase #3	$16.49	9.464%	$18.0506	$18.05	$18.05	$18.10
Purchase #4	$92.27	8.518%	$100.1296	$100.13	$100.15	$100.10
Purchase #5	$144.61	6.321%	$153.7508	$153.75	$153.75	$153.80
Purchase #6	$167.55	9.487%	$183.4455	$183.45	$183.45	$183.40
Purchase #7	$48.94	5.416%	$51.5906	$51.59	$51.60	$51.60
7 purchase totals =	$801.02		$851.9603	$851.96	$852.00	$852.00