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	$212.88	9.713%	$233.557	$233.56	$233.55	$233.60
Purchase #2	$32.77	4.716%	$34.3154	$34.32	$34.30	$34.30
Purchase #3	$186.70	7.260%	$200.2544	$200.25	$200.25	$200.30
Purchase #4	$247.35	3.189%	$255.238	$255.24	$255.25	$255.20
Purchase #5	$249.87	4.694%	$261.5989	$261.60	$261.60	$261.60
Purchase #6	$128.77	13.457%	$146.0986	$146.10	$146.10	$146.10
Purchase #7	$149.55	10.208%	$164.8161	$164.82	$164.80	$164.80
7 purchase totals =	$1,207.89		$1,295.8784	$1,295.89	$1,295.85	$1,295.90