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	$103.83	11.719%	$115.9978	$116.00	$116.00	$116.00
Purchase #2	$120.31	9.326%	$131.5301	$131.53	$131.55	$131.50
Purchase #3	$45.27	4.418%	$47.27	$47.27	$47.25	$47.30
Purchase #4	$55.89	7.296%	$59.9677	$59.97	$59.95	$60.00
Purchase #5	$142.80	4.751%	$149.5844	$149.58	$149.60	$149.60
Purchase #6	$55.38	7.423%	$59.4909	$59.49	$59.50	$59.50
Purchase #7	$117.89	12.231%	$132.3091	$132.31	$132.30	$132.30
7 purchase totals =	$641.37		$696.1500	$696.15	$696.15	$696.20