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	$133.83	10.271%	$147.5757	$147.58	$147.60	$147.60
Purchase #2	$132.52	13.704%	$150.6805	$150.68	$150.70	$150.70
Purchase #3	$166.83	3.520%	$172.7024	$172.70	$172.70	$172.70
Purchase #4	$178.55	3.800%	$185.3349	$185.33	$185.35	$185.30
Purchase #5	$161.45	11.372%	$179.8101	$179.81	$179.80	$179.80
Purchase #6	$45.52	12.218%	$51.0816	$51.08	$51.10	$51.10
Purchase #7	$162.54	13.810%	$184.9868	$184.99	$185.00	$185.00
7 purchase totals =	$981.24		$1,072.1720	$1,072.17	$1,072.25	$1,072.20