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	$105.38	3.476%	$109.043	$109.04	$109.05	$109.00
Purchase #2	$143.86	10.165%	$158.4834	$158.48	$158.50	$158.50
Purchase #3	$131.87	9.293%	$144.1247	$144.12	$144.10	$144.10
Purchase #4	$238.88	9.732%	$262.1278	$262.13	$262.15	$262.10
Purchase #5	$44.80	13.800%	$50.9824	$50.98	$51.00	$51.00
Purchase #6	$208.83	5.524%	$220.3658	$220.37	$220.35	$220.40
Purchase #7	$127.65	4.446%	$133.3253	$133.33	$133.35	$133.30
7 purchase totals =	$1,001.27		$1,078.4524	$1,078.45	$1,078.50	$1,078.40