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	$145.42	13.683%	$165.3178	$165.32	$165.30	$165.30
Purchase #2	$56.99	7.428%	$61.2232	$61.22	$61.20	$61.20
Purchase #3	$228.86	5.492%	$241.429	$241.43	$241.45	$241.40
Purchase #4	$108.41	5.233%	$114.0831	$114.08	$114.10	$114.10
Purchase #5	$192.77	12.760%	$217.3675	$217.37	$217.35	$217.40
Purchase #6	$38.61	3.465%	$39.9478	$39.95	$39.95	$39.90
Purchase #7	$238.67	3.274%	$246.4841	$246.48	$246.50	$246.50
7 purchase totals =	$1,009.73		$1,085.8525	$1,085.85	$1,085.85	$1,085.80