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	$100.28	11.140%	$111.4512	$111.45	$111.45	$111.50
Purchase #2	$132.28	9.688%	$145.0953	$145.10	$145.10	$145.10
Purchase #3	$12.65	12.418%	$14.2209	$14.22	$14.20	$14.20
Purchase #4	$167.86	11.215%	$186.6855	$186.69	$186.70	$186.70
Purchase #5	$25.78	5.757%	$27.2642	$27.26	$27.25	$27.30
Purchase #6	$89.32	13.264%	$101.1674	$101.17	$101.15	$101.20
Purchase #7	$146.75	6.776%	$156.6938	$156.69	$156.70	$156.70
7 purchase totals =	$674.92		$742.5783	$742.58	$742.55	$742.70