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	$89.29	10.467%	$98.636	$98.64	$98.65	$98.60
Purchase #2	$250.97	11.713%	$280.3661	$280.37	$280.35	$280.40
Purchase #3	$234.64	12.722%	$264.4909	$264.49	$264.50	$264.50
Purchase #4	$198.40	11.122%	$220.466	$220.47	$220.45	$220.50
Purchase #5	$156.32	11.196%	$173.8216	$173.82	$173.80	$173.80
Purchase #6	$196.38	6.353%	$208.856	$208.86	$208.85	$208.90
Purchase #7	$17.95	9.121%	$19.5872	$19.59	$19.60	$19.60
7 purchase totals =	$1,143.95		$1,266.2238	$1,266.24	$1,266.20	$1,266.30