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	$31.32	8.225%	$33.8961	$33.90	$33.90	$33.90
Purchase #2	$119.97	3.300%	$123.929	$123.93	$123.95	$123.90
Purchase #3	$118.40	5.376%	$124.7652	$124.77	$124.75	$124.80
Purchase #4	$248.89	9.512%	$272.5644	$272.56	$272.55	$272.60
Purchase #5	$58.94	5.756%	$62.3326	$62.33	$62.35	$62.30
Purchase #6	$40.94	7.351%	$43.9495	$43.95	$43.95	$43.90
Purchase #7	$41.47	12.379%	$46.6036	$46.60	$46.60	$46.60
7 purchase totals =	$659.93		$708.0404	$708.04	$708.05	$708.00