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	$93.25	8.212%	$100.9077	$100.91	$100.90	$100.90
Purchase #2	$129.51	12.436%	$145.6159	$145.62	$145.60	$145.60
Purchase #3	$153.55	12.273%	$172.3952	$172.40	$172.40	$172.40
Purchase #4	$149.85	8.293%	$162.2771	$162.28	$162.30	$162.30
Purchase #5	$154.78	8.837%	$168.4579	$168.46	$168.45	$168.50
Purchase #6	$192.61	3.493%	$199.3379	$199.34	$199.35	$199.30
Purchase #7	$111.75	7.338%	$119.9502	$119.95	$119.95	$120.00
7 purchase totals =	$985.30		$1,068.9419	$1,068.96	$1,068.95	$1,069.00