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	$98.66	13.459%	$111.9386	$111.94	$111.95	$111.90
Purchase #2	$103.83	7.583%	$111.7034	$111.70	$111.70	$111.70
Purchase #3	$78.75	8.195%	$85.2036	$85.20	$85.20	$85.20
Purchase #4	$17.58	10.268%	$19.3851	$19.39	$19.40	$19.40
Purchase #5	$155.31	10.295%	$171.2992	$171.30	$171.30	$171.30
Purchase #6	$64.43	7.307%	$69.1379	$69.14	$69.15	$69.10
Purchase #7	$211.62	4.379%	$220.8868	$220.89	$220.90	$220.90
7 purchase totals =	$730.18		$789.5546	$789.56	$789.60	$789.50