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	$137.79	4.359%	$143.7963	$143.80	$143.80	$143.80
Purchase #2	$226.35	5.318%	$238.3873	$238.39	$238.40	$238.40
Purchase #3	$49.61	8.522%	$53.8378	$53.84	$53.85	$53.80
Purchase #4	$108.80	5.603%	$114.8961	$114.90	$114.90	$114.90
Purchase #5	$172.86	12.678%	$194.7752	$194.78	$194.80	$194.80
Purchase #6	$94.63	6.610%	$100.885	$100.89	$100.90	$100.90
Purchase #7	$213.78	3.547%	$221.3628	$221.36	$221.35	$221.40
7 purchase totals =	$1,003.82		$1,067.9405	$1,067.96	$1,068.00	$1,068.00