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	$236.88	9.447%	$259.2581	$259.26	$259.25	$259.30
Purchase #2	$105.85	6.329%	$112.5492	$112.55	$112.55	$112.50
Purchase #3	$92.35	7.741%	$99.4988	$99.50	$99.50	$99.50
Purchase #4	$51.69	9.834%	$56.7732	$56.77	$56.75	$56.80
Purchase #5	$145.77	12.752%	$164.3586	$164.36	$164.35	$164.40
Purchase #6	$33.64	4.211%	$35.0566	$35.06	$35.05	$35.10
Purchase #7	$198.94	13.139%	$225.0787	$225.08	$225.10	$225.10
7 purchase totals =	$865.12		$952.5732	$952.58	$952.55	$952.70