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	$49.35	11.246%	$54.8999	$54.90	$54.90	$54.90
Purchase #2	$173.83	7.379%	$186.6569	$186.66	$186.65	$186.70
Purchase #3	$217.29	10.637%	$240.4031	$240.40	$240.40	$240.40
Purchase #4	$185.43	13.561%	$210.5762	$210.58	$210.60	$210.60
Purchase #5	$189.69	12.747%	$213.8698	$213.87	$213.85	$213.90
Purchase #6	$44.51	4.417%	$46.476	$46.48	$46.50	$46.50
Purchase #7	$241.70	5.744%	$255.5832	$255.58	$255.60	$255.60
7 purchase totals =	$1,101.80		$1,208.4651	$1,208.47	$1,208.50	$1,208.60