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	$114.51	7.779%	$123.4177	$123.42	$123.40	$123.40
Purchase #2	$210.31	3.364%	$217.3848	$217.38	$217.40	$217.40
Purchase #3	$104.47	4.767%	$109.4501	$109.45	$109.45	$109.50
Purchase #4	$15.42	12.636%	$17.3685	$17.37	$17.35	$17.40
Purchase #5	$153.86	4.345%	$160.5452	$160.55	$160.55	$160.50
Purchase #6	$46.58	4.150%	$48.5131	$48.51	$48.50	$48.50
Purchase #7	$28.93	12.455%	$32.5332	$32.53	$32.55	$32.50
7 purchase totals =	$674.08		$709.2126	$709.21	$709.20	$709.20