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	$42.76	8.636%	$46.4528	$46.45	$46.45	$46.50
Purchase #2	$52.70	12.121%	$59.0878	$59.09	$59.10	$59.10
Purchase #3	$136.30	6.619%	$145.3217	$145.32	$145.30	$145.30
Purchase #4	$88.98	7.253%	$95.4337	$95.43	$95.45	$95.40
Purchase #5	$131.74	4.400%	$137.5366	$137.54	$137.55	$137.50
Purchase #6	$173.89	7.811%	$187.4725	$187.47	$187.45	$187.50
Purchase #7	$72.87	13.491%	$82.7009	$82.70	$82.70	$82.70
7 purchase totals =	$699.24		$754.0060	$754.00	$754.00	$754.00