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	$161.57	12.733%	$182.1427	$182.14	$182.15	$182.10
Purchase #2	$56.60	5.564%	$59.7492	$59.75	$59.75	$59.70
Purchase #3	$158.94	6.279%	$168.9198	$168.92	$168.90	$168.90
Purchase #4	$90.69	11.106%	$100.762	$100.76	$100.75	$100.80
Purchase #5	$69.53	13.163%	$78.6822	$78.68	$78.70	$78.70
Purchase #6	$168.28	3.126%	$173.5404	$173.54	$173.55	$173.50
Purchase #7	$90.87	12.870%	$102.565	$102.57	$102.55	$102.60
7 purchase totals =	$796.48		$866.3613	$866.36	$866.35	$866.30