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	$168.79	6.786%	$180.2441	$180.24	$180.25	$180.20
Purchase #2	$69.25	6.626%	$73.8385	$73.84	$73.85	$73.80
Purchase #3	$178.29	6.695%	$190.2265	$190.23	$190.25	$190.20
Purchase #4	$13.27	4.321%	$13.8434	$13.84	$13.85	$13.80
Purchase #5	$41.78	4.785%	$43.7792	$43.78	$43.80	$43.80
Purchase #6	$102.63	8.279%	$111.1267	$111.13	$111.15	$111.10
Purchase #7	$13.99	11.462%	$15.5935	$15.59	$15.60	$15.60
7 purchase totals =	$588.00		$628.6519	$628.65	$628.75	$628.50