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	$156.73	4.821%	$164.286	$164.29	$164.30	$164.30
Purchase #2	$200.40	11.521%	$223.4881	$223.49	$223.50	$223.50
Purchase #3	$60.37	4.491%	$63.0812	$63.08	$63.10	$63.10
Purchase #4	$140.26	9.352%	$153.3771	$153.38	$153.40	$153.40
Purchase #5	$225.57	13.863%	$256.8408	$256.84	$256.85	$256.80
Purchase #6	$38.74	11.441%	$43.1722	$43.17	$43.15	$43.20
Purchase #7	$129.83	7.686%	$139.8087	$139.81	$139.80	$139.80
7 purchase totals =	$951.90		$1,044.0541	$1,044.06	$1,044.10	$1,044.10