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	$218.32	9.172%	$238.3443	$238.34	$238.35	$238.30
Purchase #2	$111.62	9.174%	$121.86	$121.86	$121.85	$121.90
Purchase #3	$155.29	11.389%	$172.976	$172.98	$173.00	$173.00
Purchase #4	$169.72	5.403%	$178.89	$178.89	$178.90	$178.90
Purchase #5	$48.76	13.772%	$55.4752	$55.48	$55.50	$55.50
Purchase #6	$150.68	7.266%	$161.6284	$161.63	$161.65	$161.60
Purchase #7	$225.98	13.651%	$256.8285	$256.83	$256.85	$256.80
7 purchase totals =	$1,080.37		$1,186.0024	$1,186.01	$1,186.10	$1,186.00