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	$190.81	13.673%	$216.8995	$216.90	$216.90	$216.90
Purchase #2	$175.41	8.712%	$190.6917	$190.69	$190.70	$190.70
Purchase #3	$108.41	13.797%	$123.3673	$123.37	$123.35	$123.40
Purchase #4	$49.27	4.551%	$51.5123	$51.51	$51.50	$51.50
Purchase #5	$14.52	7.488%	$15.6073	$15.61	$15.60	$15.60
Purchase #6	$124.26	5.389%	$130.9564	$130.96	$130.95	$131.00
Purchase #7	$111.30	7.780%	$119.9591	$119.96	$119.95	$120.00
7 purchase totals =	$773.98		$848.9936	$849.00	$848.95	$849.10