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	$113.34	5.776%	$119.8865	$119.89	$119.90	$119.90
Purchase #2	$92.76	11.587%	$103.5081	$103.51	$103.50	$103.50
Purchase #3	$196.75	6.867%	$210.2608	$210.26	$210.25	$210.30
Purchase #4	$184.51	4.467%	$192.7521	$192.75	$192.75	$192.80
Purchase #5	$131.51	7.656%	$141.5784	$141.58	$141.60	$141.60
Purchase #6	$185.56	10.248%	$204.5762	$204.58	$204.60	$204.60
Purchase #7	$241.81	9.836%	$265.5944	$265.59	$265.60	$265.60
7 purchase totals =	$1,146.24		$1,238.1565	$1,238.16	$1,238.20	$1,238.30