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	$106.89	10.398%	$118.0044	$118.00	$118.00	$118.00
Purchase #2	$233.88	9.502%	$256.1033	$256.10	$256.10	$256.10
Purchase #3	$246.96	5.656%	$260.9281	$260.93	$260.95	$260.90
Purchase #4	$10.78	10.740%	$11.9378	$11.94	$11.95	$11.90
Purchase #5	$97.52	5.680%	$103.0591	$103.06	$103.05	$103.10
Purchase #6	$11.54	3.549%	$11.9496	$11.95	$11.95	$11.90
Purchase #7	$109.58	12.535%	$123.3159	$123.32	$123.30	$123.30
7 purchase totals =	$817.15		$885.2982	$885.30	$885.30	$885.20