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	$213.50	6.571%	$227.5291	$227.53	$227.55	$227.50
Purchase #2	$97.39	6.359%	$103.583	$103.58	$103.60	$103.60
Purchase #3	$210.54	3.491%	$217.89	$217.89	$217.90	$217.90
Purchase #4	$105.67	10.534%	$116.8013	$116.80	$116.80	$116.80
Purchase #5	$88.64	13.859%	$100.9246	$100.92	$100.90	$100.90
Purchase #6	$94.63	9.191%	$103.3274	$103.33	$103.35	$103.30
Purchase #7	$36.77	13.285%	$41.6549	$41.65	$41.65	$41.70
7 purchase totals =	$847.14		$911.7103	$911.70	$911.75	$911.70