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	$164.27	11.709%	$183.5044	$183.50	$183.50	$183.50
Purchase #2	$139.49	13.604%	$158.4662	$158.47	$158.45	$158.50
Purchase #3	$148.39	6.872%	$158.5874	$158.59	$158.60	$158.60
Purchase #4	$128.28	10.423%	$141.6506	$141.65	$141.65	$141.70
Purchase #5	$215.86	5.491%	$227.7129	$227.71	$227.70	$227.70
Purchase #6	$176.89	3.757%	$183.5358	$183.54	$183.55	$183.50
Purchase #7	$26.98	4.529%	$28.2019	$28.20	$28.20	$28.20
7 purchase totals =	$1,000.16		$1,081.6592	$1,081.66	$1,081.65	$1,081.70