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	$214.59	12.584%	$241.594	$241.59	$241.60	$241.60
Purchase #2	$161.30	7.542%	$173.4652	$173.47	$173.45	$173.50
Purchase #3	$13.80	12.483%	$15.5227	$15.52	$15.50	$15.50
Purchase #4	$40.36	6.446%	$42.9616	$42.96	$42.95	$43.00
Purchase #5	$110.62	11.620%	$123.474	$123.47	$123.45	$123.50
Purchase #6	$20.33	4.639%	$21.2731	$21.27	$21.25	$21.30
Purchase #7	$236.64	9.258%	$258.5481	$258.55	$258.55	$258.50
7 purchase totals =	$797.64		$876.8387	$876.83	$876.75	$876.90