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	$241.70	9.233%	$264.0162	$264.02	$264.00	$264.00
Purchase #2	$42.61	5.613%	$45.0017	$45.00	$45.00	$45.00
Purchase #3	$248.54	12.659%	$280.0027	$280.00	$280.00	$280.00
Purchase #4	$203.88	4.866%	$213.8008	$213.80	$213.80	$213.80
Purchase #5	$124.44	6.470%	$132.4913	$132.49	$132.50	$132.50
Purchase #6	$147.41	12.770%	$166.2343	$166.23	$166.25	$166.20
Purchase #7	$149.82	7.316%	$160.7808	$160.78	$160.80	$160.80
7 purchase totals =	$1,158.40		$1,262.3278	$1,262.32	$1,262.35	$1,262.30