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	$184.95	10.432%	$204.244	$204.24	$204.25	$204.20
Purchase #2	$138.52	7.449%	$148.8384	$148.84	$148.85	$148.80
Purchase #3	$187.83	4.548%	$196.3725	$196.37	$196.35	$196.40
Purchase #4	$97.25	3.818%	$100.963	$100.96	$100.95	$101.00
Purchase #5	$41.51	7.602%	$44.6656	$44.67	$44.65	$44.70
Purchase #6	$178.48	10.339%	$196.933	$196.93	$196.95	$196.90
Purchase #7	$240.96	4.822%	$252.5791	$252.58	$252.60	$252.60
7 purchase totals =	$1,069.50		$1,144.5956	$1,144.59	$1,144.60	$1,144.60