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	$78.28	10.647%	$86.6145	$86.61	$86.60	$86.60
Purchase #2	$153.67	12.523%	$172.9141	$172.91	$172.90	$172.90
Purchase #3	$33.95	7.134%	$36.372	$36.37	$36.35	$36.40
Purchase #4	$152.90	11.149%	$169.9468	$169.95	$169.95	$169.90
Purchase #5	$18.42	13.380%	$20.8846	$20.88	$20.90	$20.90
Purchase #6	$33.69	7.165%	$36.1039	$36.10	$36.10	$36.10
Purchase #7	$179.29	9.446%	$196.2257	$196.23	$196.25	$196.20
7 purchase totals =	$650.20		$719.0616	$719.05	$719.05	$719.00