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	$126.73	3.759%	$131.4938	$131.49	$131.50	$131.50
Purchase #2	$230.25	4.812%	$241.3296	$241.33	$241.35	$241.30
Purchase #3	$121.69	5.295%	$128.1335	$128.13	$128.15	$128.10
Purchase #4	$236.80	4.249%	$246.8616	$246.86	$246.85	$246.90
Purchase #5	$45.44	7.582%	$48.8853	$48.89	$48.90	$48.90
Purchase #6	$124.51	10.429%	$137.4951	$137.50	$137.50	$137.50
Purchase #7	$215.84	8.232%	$233.6079	$233.61	$233.60	$233.60
7 purchase totals =	$1,101.26		$1,167.8068	$1,167.81	$1,167.85	$1,167.80