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	$103.64	8.464%	$112.4121	$112.41	$112.40	$112.40
Purchase #2	$77.79	10.845%	$86.2263	$86.23	$86.25	$86.20
Purchase #3	$196.83	6.392%	$209.4114	$209.41	$209.40	$209.40
Purchase #4	$86.58	10.253%	$95.457	$95.46	$95.45	$95.50
Purchase #5	$149.57	8.712%	$162.6005	$162.60	$162.60	$162.60
Purchase #6	$34.87	10.295%	$38.4599	$38.46	$38.45	$38.50
Purchase #7	$238.64	7.493%	$256.5213	$256.52	$256.50	$256.50
7 purchase totals =	$887.92		$961.0885	$961.09	$961.05	$961.10