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	$145.59	13.542%	$165.3058	$165.31	$165.30	$165.30
Purchase #2	$100.65	6.161%	$106.851	$106.85	$106.85	$106.90
Purchase #3	$64.27	12.630%	$72.3873	$72.39	$72.40	$72.40
Purchase #4	$32.85	5.359%	$34.6104	$34.61	$34.60	$34.60
Purchase #5	$20.80	12.853%	$23.4734	$23.47	$23.45	$23.50
Purchase #6	$114.26	3.397%	$118.1414	$118.14	$118.15	$118.10
Purchase #7	$190.59	4.217%	$198.6272	$198.63	$198.65	$198.60
7 purchase totals =	$669.01		$719.3965	$719.40	$719.40	$719.40