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	$61.66	7.666%	$66.3869	$66.39	$66.40	$66.40
Purchase #2	$247.36	4.746%	$259.0997	$259.10	$259.10	$259.10
Purchase #3	$115.66	10.564%	$127.8783	$127.88	$127.90	$127.90
Purchase #4	$71.34	10.184%	$78.6053	$78.61	$78.60	$78.60
Purchase #5	$172.89	4.718%	$181.047	$181.05	$181.05	$181.00
Purchase #6	$208.40	8.105%	$225.2908	$225.29	$225.30	$225.30
Purchase #7	$206.45	9.162%	$225.3649	$225.36	$225.35	$225.40
7 purchase totals =	$1,083.76		$1,163.6729	$1,163.68	$1,163.70	$1,163.70