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	$249.52	7.381%	$267.9371	$267.94	$267.95	$267.90
Purchase #2	$184.36	4.398%	$192.4682	$192.47	$192.45	$192.50
Purchase #3	$220.27	10.787%	$244.0305	$244.03	$244.05	$244.00
Purchase #4	$104.92	9.523%	$114.9115	$114.91	$114.90	$114.90
Purchase #5	$64.75	11.815%	$72.4002	$72.40	$72.40	$72.40
Purchase #6	$171.27	13.566%	$194.5045	$194.50	$194.50	$194.50
Purchase #7	$56.36	10.605%	$62.337	$62.34	$62.35	$62.30
7 purchase totals =	$1,051.45		$1,148.5890	$1,148.59	$1,148.60	$1,148.50