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	$183.37	13.752%	$208.587	$208.59	$208.60	$208.60
Purchase #2	$219.70	5.213%	$231.153	$231.15	$231.15	$231.20
Purchase #3	$166.82	3.650%	$172.9089	$172.91	$172.90	$172.90
Purchase #4	$35.93	3.112%	$37.0481	$37.05	$37.05	$37.00
Purchase #5	$65.86	4.209%	$68.632	$68.63	$68.65	$68.60
Purchase #6	$234.41	9.394%	$256.4305	$256.43	$256.45	$256.40
Purchase #7	$122.62	12.174%	$137.5478	$137.55	$137.55	$137.50
7 purchase totals =	$1,028.71		$1,112.3073	$1,112.31	$1,112.35	$1,112.20