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	$233.73	12.147%	$262.1212	$262.12	$262.10	$262.10
Purchase #2	$220.80	9.255%	$241.235	$241.24	$241.25	$241.20
Purchase #3	$70.29	9.174%	$76.7384	$76.74	$76.75	$76.70
Purchase #4	$91.51	9.691%	$100.3782	$100.38	$100.40	$100.40
Purchase #5	$132.54	13.800%	$150.8305	$150.83	$150.85	$150.80
Purchase #6	$153.95	3.847%	$159.8725	$159.87	$159.85	$159.90
Purchase #7	$92.78	5.692%	$98.061	$98.06	$98.05	$98.10
7 purchase totals =	$995.60		$1,089.2368	$1,089.24	$1,089.25	$1,089.20