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	$242.69	9.730%	$266.3037	$266.30	$266.30	$266.30
Purchase #2	$54.47	9.522%	$59.6566	$59.66	$59.65	$59.70
Purchase #3	$167.28	4.540%	$174.8745	$174.87	$174.85	$174.90
Purchase #4	$77.43	11.196%	$86.0991	$86.10	$86.10	$86.10
Purchase #5	$30.87	8.452%	$33.4791	$33.48	$33.50	$33.50
Purchase #6	$31.31	3.291%	$32.3404	$32.34	$32.35	$32.30
Purchase #7	$205.95	8.246%	$222.9326	$222.93	$222.95	$222.90
7 purchase totals =	$810.00		$875.6860	$875.68	$875.70	$875.70