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	$51.42	5.789%	$54.3967	$54.40	$54.40	$54.40
Purchase #2	$234.69	3.244%	$242.3033	$242.30	$242.30	$242.30
Purchase #3	$191.94	4.636%	$200.8383	$200.84	$200.85	$200.80
Purchase #4	$79.91	3.213%	$82.4775	$82.48	$82.50	$82.50
Purchase #5	$72.97	11.425%	$81.3068	$81.31	$81.30	$81.30
Purchase #6	$56.80	6.325%	$60.3926	$60.39	$60.40	$60.40
Purchase #7	$248.90	5.598%	$262.8334	$262.83	$262.85	$262.80
7 purchase totals =	$936.63		$984.5486	$984.55	$984.60	$984.50