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	$87.46	5.755%	$92.4933	$92.49	$92.50	$92.50
Purchase #2	$143.94	7.374%	$154.5541	$154.55	$154.55	$154.60
Purchase #3	$228.49	9.823%	$250.9346	$250.93	$250.95	$250.90
Purchase #4	$100.40	11.129%	$111.5735	$111.57	$111.55	$111.60
Purchase #5	$143.35	13.795%	$163.1251	$163.13	$163.15	$163.10
Purchase #6	$63.51	3.328%	$65.6236	$65.62	$65.60	$65.60
Purchase #7	$161.25	4.775%	$168.9497	$168.95	$168.95	$168.90
7 purchase totals =	$928.40		$1,007.2539	$1,007.24	$1,007.25	$1,007.20