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	$59.60	9.367%	$65.1827	$65.18	$65.20	$65.20
Purchase #2	$117.27	7.661%	$126.2541	$126.25	$126.25	$126.30
Purchase #3	$62.33	11.641%	$69.5858	$69.59	$69.60	$69.60
Purchase #4	$76.58	9.546%	$83.8903	$83.89	$83.90	$83.90
Purchase #5	$216.73	11.363%	$241.357	$241.36	$241.35	$241.40
Purchase #6	$199.37	11.481%	$222.2597	$222.26	$222.25	$222.30
Purchase #7	$164.95	4.458%	$172.3035	$172.30	$172.30	$172.30
7 purchase totals =	$896.83		$980.8331	$980.83	$980.85	$981.00