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	$225.39	7.436%	$242.15	$242.15	$242.15	$242.20
Purchase #2	$213.58	10.720%	$236.4758	$236.48	$236.50	$236.50
Purchase #3	$228.53	11.691%	$255.2474	$255.25	$255.25	$255.20
Purchase #4	$33.86	12.702%	$38.1609	$38.16	$38.15	$38.20
Purchase #5	$238.55	9.523%	$261.2671	$261.27	$261.25	$261.30
Purchase #6	$58.96	13.536%	$66.9408	$66.94	$66.95	$66.90
Purchase #7	$153.56	12.784%	$173.1911	$173.19	$173.20	$173.20
7 purchase totals =	$1,152.43		$1,273.4331	$1,273.44	$1,273.45	$1,273.50