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	$95.93	8.845%	$104.415	$104.42	$104.40	$104.40
Purchase #2	$198.62	5.854%	$210.2472	$210.25	$210.25	$210.20
Purchase #3	$153.32	9.839%	$168.4052	$168.41	$168.40	$168.40
Purchase #4	$54.28	5.527%	$57.2801	$57.28	$57.30	$57.30
Purchase #5	$244.37	5.149%	$256.9526	$256.95	$256.95	$257.00
Purchase #6	$82.25	11.461%	$91.6767	$91.68	$91.70	$91.70
Purchase #7	$15.39	3.240%	$15.8886	$15.89	$15.90	$15.90
7 purchase totals =	$844.16		$904.8654	$904.88	$904.90	$904.90