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	$72.59	12.716%	$81.8205	$81.82	$81.80	$81.80
Purchase #2	$101.52	11.439%	$113.1329	$113.13	$113.15	$113.10
Purchase #3	$66.44	8.299%	$71.9539	$71.95	$71.95	$72.00
Purchase #4	$250.60	6.373%	$266.5707	$266.57	$266.55	$266.60
Purchase #5	$133.93	12.797%	$151.069	$151.07	$151.05	$151.10
Purchase #6	$240.57	8.734%	$261.5814	$261.58	$261.60	$261.60
Purchase #7	$172.96	13.712%	$196.6763	$196.68	$196.70	$196.70
7 purchase totals =	$1,038.61		$1,142.8047	$1,142.80	$1,142.80	$1,142.90