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	$92.89	12.126%	$104.1538	$104.15	$104.15	$104.20
Purchase #2	$166.45	12.759%	$187.6874	$187.69	$187.70	$187.70
Purchase #3	$85.91	4.209%	$89.526	$89.53	$89.55	$89.50
Purchase #4	$39.62	5.471%	$41.7876	$41.79	$41.80	$41.80
Purchase #5	$142.53	11.328%	$158.6758	$158.68	$158.70	$158.70
Purchase #6	$121.99	12.627%	$137.3937	$137.39	$137.40	$137.40
Purchase #7	$207.39	9.867%	$227.8532	$227.85	$227.85	$227.90
7 purchase totals =	$856.78		$947.0775	$947.08	$947.15	$947.20