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	$198.38	6.333%	$210.9434	$210.94	$210.95	$210.90
Purchase #2	$30.34	7.353%	$32.5709	$32.57	$32.55	$32.60
Purchase #3	$137.95	4.723%	$144.4654	$144.47	$144.45	$144.50
Purchase #4	$43.27	3.119%	$44.6196	$44.62	$44.60	$44.60
Purchase #5	$108.75	13.672%	$123.6183	$123.62	$123.60	$123.60
Purchase #6	$138.61	4.163%	$144.3803	$144.38	$144.40	$144.40
Purchase #7	$232.34	8.598%	$252.3166	$252.32	$252.30	$252.30
7 purchase totals =	$889.64		$952.9145	$952.92	$952.85	$952.90