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	$226.59	7.625%	$243.8675	$243.87	$243.85	$243.90
Purchase #2	$29.90	6.652%	$31.8889	$31.89	$31.90	$31.90
Purchase #3	$10.60	12.681%	$11.9442	$11.94	$11.95	$11.90
Purchase #4	$40.67	8.192%	$44.0017	$44.00	$44.00	$44.00
Purchase #5	$46.64	11.142%	$51.8366	$51.84	$51.85	$51.80
Purchase #6	$153.47	7.680%	$165.2565	$165.26	$165.25	$165.30
Purchase #7	$97.51	12.147%	$109.3545	$109.35	$109.35	$109.40
7 purchase totals =	$605.38		$658.1499	$658.15	$658.15	$658.20