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	$10.83	5.772%	$11.4551	$11.46	$11.45	$11.50
Purchase #2	$167.78	9.847%	$184.3013	$184.30	$184.30	$184.30
Purchase #3	$104.32	8.212%	$112.8868	$112.89	$112.90	$112.90
Purchase #4	$241.86	13.332%	$274.1048	$274.10	$274.10	$274.10
Purchase #5	$16.64	13.168%	$18.8312	$18.83	$18.85	$18.80
Purchase #6	$43.32	6.793%	$46.2627	$46.26	$46.25	$46.30
Purchase #7	$121.42	3.456%	$125.6163	$125.62	$125.60	$125.60
7 purchase totals =	$706.17		$773.4582	$773.46	$773.45	$773.50