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	$222.61	9.505%	$243.7691	$243.77	$243.75	$243.80
Purchase #2	$55.47	13.671%	$63.0533	$63.05	$63.05	$63.10
Purchase #3	$55.83	6.771%	$59.6102	$59.61	$59.60	$59.60
Purchase #4	$68.76	4.822%	$72.0756	$72.08	$72.10	$72.10
Purchase #5	$239.43	3.798%	$248.5236	$248.52	$248.50	$248.50
Purchase #6	$112.80	13.312%	$127.8159	$127.82	$127.80	$127.80
Purchase #7	$167.35	5.440%	$176.4538	$176.45	$176.45	$176.50
7 purchase totals =	$922.25		$991.3015	$991.30	$991.25	$991.40