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	$239.38	4.469%	$250.0779	$250.08	$250.10	$250.10
Purchase #2	$94.47	10.662%	$104.5424	$104.54	$104.55	$104.50
Purchase #3	$78.40	5.373%	$82.6124	$82.61	$82.60	$82.60
Purchase #4	$41.30	3.627%	$42.798	$42.80	$42.80	$42.80
Purchase #5	$208.54	13.581%	$236.8618	$236.86	$236.85	$236.90
Purchase #6	$159.39	13.380%	$180.7164	$180.72	$180.70	$180.70
Purchase #7	$38.29	12.310%	$43.0035	$43.00	$43.00	$43.00
7 purchase totals =	$859.77		$940.6124	$940.61	$940.60	$940.60