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	$40.60	8.464%	$44.0364	$44.04	$44.05	$44.00
Purchase #2	$9.37	9.209%	$10.2329	$10.23	$10.25	$10.20
Purchase #3	$69.84	12.677%	$78.6936	$78.69	$78.70	$78.70
Purchase #4	$39.86	13.280%	$45.1534	$45.15	$45.15	$45.20
Purchase #5	$7.33	6.789%	$7.8276	$7.83	$7.85	$7.80
Purchase #6	$55.54	4.180%	$57.8616	$57.86	$57.85	$57.90
Purchase #7	$38.73	7.784%	$41.7447	$41.74	$41.75	$41.70
7 purchase totals =	$261.27		$285.5502	$285.54	$285.60	$285.50