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	$245.59	13.812%	$279.5109	$279.51	$279.50	$279.50
Purchase #2	$89.60	12.268%	$100.5921	$100.59	$100.60	$100.60
Purchase #3	$13.29	8.330%	$14.3971	$14.40	$14.40	$14.40
Purchase #4	$166.70	3.163%	$171.9727	$171.97	$171.95	$172.00
Purchase #5	$66.34	8.415%	$71.9225	$71.92	$71.90	$71.90
Purchase #6	$175.93	13.313%	$199.3516	$199.35	$199.35	$199.40
Purchase #7	$110.45	3.177%	$113.959	$113.96	$113.95	$114.00
7 purchase totals =	$867.90		$951.7059	$951.70	$951.65	$951.80