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	$125.57	13.770%	$142.861	$142.86	$142.85	$142.90
Purchase #2	$179.44	4.356%	$187.2564	$187.26	$187.25	$187.30
Purchase #3	$64.81	5.823%	$68.5839	$68.58	$68.60	$68.60
Purchase #4	$134.87	5.502%	$142.2905	$142.29	$142.30	$142.30
Purchase #5	$197.34	10.189%	$217.447	$217.45	$217.45	$217.40
Purchase #6	$72.61	8.620%	$78.869	$78.87	$78.85	$78.90
Purchase #7	$203.40	13.227%	$230.3037	$230.30	$230.30	$230.30
7 purchase totals =	$978.04		$1,067.6115	$1,067.61	$1,067.60	$1,067.70