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	$154.45	6.686%	$164.7765	$164.78	$164.80	$164.80
Purchase #2	$202.57	3.835%	$210.3386	$210.34	$210.35	$210.30
Purchase #3	$39.27	10.650%	$43.4523	$43.45	$43.45	$43.50
Purchase #4	$156.35	10.588%	$172.9043	$172.90	$172.90	$172.90
Purchase #5	$146.73	9.454%	$160.6019	$160.60	$160.60	$160.60
Purchase #6	$72.85	5.434%	$76.8087	$76.81	$76.80	$76.80
Purchase #7	$227.32	13.858%	$258.822	$258.82	$258.80	$258.80
7 purchase totals =	$999.54		$1,087.7043	$1,087.70	$1,087.70	$1,087.70