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	$59.78	11.803%	$66.8358	$66.84	$66.85	$66.80
Purchase #2	$153.46	5.727%	$162.2487	$162.25	$162.25	$162.20
Purchase #3	$191.26	12.476%	$215.1216	$215.12	$215.10	$215.10
Purchase #4	$108.62	3.221%	$112.1187	$112.12	$112.10	$112.10
Purchase #5	$134.79	6.212%	$143.1632	$143.16	$143.15	$143.20
Purchase #6	$60.68	10.194%	$66.8657	$66.87	$66.85	$66.90
Purchase #7	$103.81	5.534%	$109.5548	$109.55	$109.55	$109.60
7 purchase totals =	$812.40		$875.9085	$875.91	$875.85	$875.90