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	$147.37	11.284%	$163.9992	$164.00	$164.00	$164.00
Purchase #2	$64.34	10.257%	$70.9394	$70.94	$70.95	$70.90
Purchase #3	$107.64	10.131%	$118.545	$118.55	$118.55	$118.50
Purchase #4	$197.88	13.501%	$224.5958	$224.60	$224.60	$224.60
Purchase #5	$106.98	4.426%	$111.7149	$111.71	$111.70	$111.70
Purchase #6	$12.78	10.610%	$14.136	$14.14	$14.15	$14.10
Purchase #7	$162.90	3.120%	$167.9825	$167.98	$168.00	$168.00
7 purchase totals =	$799.89		$871.9128	$871.92	$871.95	$871.80