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	$231.58	7.368%	$248.6428	$248.64	$248.65	$248.60
Purchase #2	$73.93	6.630%	$78.8316	$78.83	$78.85	$78.80
Purchase #3	$214.70	5.169%	$225.7978	$225.80	$225.80	$225.80
Purchase #4	$73.95	13.410%	$83.8667	$83.87	$83.85	$83.90
Purchase #5	$156.35	3.634%	$162.0318	$162.03	$162.05	$162.00
Purchase #6	$121.81	4.823%	$127.6849	$127.68	$127.70	$127.70
Purchase #7	$112.55	3.446%	$116.4285	$116.43	$116.45	$116.40
7 purchase totals =	$984.87		$1,043.2841	$1,043.28	$1,043.35	$1,043.20