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	$119.77	11.189%	$133.1711	$133.17	$133.15	$133.20
Purchase #2	$151.99	11.450%	$169.3929	$169.39	$169.40	$169.40
Purchase #3	$250.60	12.825%	$282.7395	$282.74	$282.75	$282.70
Purchase #4	$20.53	6.349%	$21.8334	$21.83	$21.85	$21.80
Purchase #5	$80.79	3.293%	$83.4504	$83.45	$83.45	$83.50
Purchase #6	$239.50	11.311%	$266.5898	$266.59	$266.60	$266.60
Purchase #7	$19.63	9.784%	$21.5506	$21.55	$21.55	$21.60
7 purchase totals =	$882.81		$978.7277	$978.72	$978.75	$978.80