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	$34.43	5.477%	$36.3157	$36.32	$36.30	$36.30
Purchase #2	$78.56	12.569%	$88.4342	$88.43	$88.45	$88.40
Purchase #3	$61.58	13.809%	$70.0836	$70.08	$70.10	$70.10
Purchase #4	$103.69	10.208%	$114.2747	$114.27	$114.25	$114.30
Purchase #5	$65.99	5.853%	$69.8524	$69.85	$69.85	$69.90
Purchase #6	$13.42	10.167%	$14.7844	$14.78	$14.80	$14.80
Purchase #7	$47.38	4.366%	$49.4486	$49.45	$49.45	$49.40
7 purchase totals =	$405.05		$443.1936	$443.18	$443.20	$443.20