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	$231.61	10.811%	$256.6494	$256.65	$256.65	$256.60
Purchase #2	$9.75	13.726%	$11.0883	$11.09	$11.10	$11.10
Purchase #3	$146.80	9.297%	$160.448	$160.45	$160.45	$160.40
Purchase #4	$246.78	6.812%	$263.5907	$263.59	$263.60	$263.60
Purchase #5	$52.33	12.811%	$59.034	$59.03	$59.05	$59.00
Purchase #6	$132.87	7.546%	$142.8964	$142.90	$142.90	$142.90
Purchase #7	$58.97	6.630%	$62.8797	$62.88	$62.90	$62.90
7 purchase totals =	$879.11		$956.5865	$956.59	$956.65	$956.50