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	$125.72	4.113%	$130.8909	$130.89	$130.90	$130.90
Purchase #2	$66.99	3.764%	$69.5115	$69.51	$69.50	$69.50
Purchase #3	$54.87	8.851%	$59.7265	$59.73	$59.75	$59.70
Purchase #4	$36.37	5.670%	$38.4322	$38.43	$38.45	$38.40
Purchase #5	$68.66	8.636%	$74.5895	$74.59	$74.60	$74.60
Purchase #6	$241.96	7.426%	$259.9279	$259.93	$259.95	$259.90
Purchase #7	$161.58	4.427%	$168.7331	$168.73	$168.75	$168.70
7 purchase totals =	$756.15		$801.8116	$801.81	$801.90	$801.70