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	$170.32	4.574%	$178.1104	$178.11	$178.10	$178.10
Purchase #2	$69.40	11.385%	$77.3012	$77.30	$77.30	$77.30
Purchase #3	$131.57	3.432%	$136.0855	$136.09	$136.10	$136.10
Purchase #4	$143.31	10.777%	$158.7545	$158.75	$158.75	$158.80
Purchase #5	$205.68	10.781%	$227.8544	$227.85	$227.85	$227.90
Purchase #6	$90.97	10.559%	$100.5755	$100.58	$100.60	$100.60
Purchase #7	$210.35	7.660%	$226.4628	$226.46	$226.45	$226.50
7 purchase totals =	$1,021.60		$1,105.1443	$1,105.14	$1,105.15	$1,105.30