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	$103.31	6.125%	$109.6377	$109.64	$109.65	$109.60
Purchase #2	$168.52	10.611%	$186.4017	$186.40	$186.40	$186.40
Purchase #3	$12.89	13.414%	$14.6191	$14.62	$14.60	$14.60
Purchase #4	$31.96	7.527%	$34.3656	$34.37	$34.35	$34.40
Purchase #5	$9.49	10.646%	$10.5003	$10.50	$10.50	$10.50
Purchase #6	$55.65	10.548%	$61.52	$61.52	$61.50	$61.50
Purchase #7	$210.99	10.789%	$233.7537	$233.75	$233.75	$233.80
7 purchase totals =	$592.81		$650.7981	$650.80	$650.75	$650.80