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	$224.87	12.516%	$253.0147	$253.01	$253.00	$253.00
Purchase #2	$141.70	12.166%	$158.9392	$158.94	$158.95	$158.90
Purchase #3	$22.52	9.220%	$24.5963	$24.60	$24.60	$24.60
Purchase #4	$210.83	10.828%	$233.6587	$233.66	$233.65	$233.70
Purchase #5	$73.78	6.158%	$78.3234	$78.32	$78.30	$78.30
Purchase #6	$174.57	7.406%	$187.4987	$187.50	$187.50	$187.50
Purchase #7	$220.76	4.226%	$230.0893	$230.09	$230.10	$230.10
7 purchase totals =	$1,069.03		$1,166.1203	$1,166.12	$1,166.10	$1,166.10