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	$108.68	7.783%	$117.1386	$117.14	$117.15	$117.10
Purchase #2	$138.81	3.232%	$143.2963	$143.30	$143.30	$143.30
Purchase #3	$66.47	8.411%	$72.0608	$72.06	$72.05	$72.10
Purchase #4	$208.97	4.364%	$218.0895	$218.09	$218.10	$218.10
Purchase #5	$99.83	11.542%	$111.3524	$111.35	$111.35	$111.40
Purchase #6	$12.80	6.566%	$13.6404	$13.64	$13.65	$13.60
Purchase #7	$35.40	3.298%	$36.5675	$36.57	$36.55	$36.60
7 purchase totals =	$670.96		$712.1455	$712.15	$712.15	$712.20