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	$160.52	8.818%	$174.6747	$174.67	$174.65	$174.70
Purchase #2	$217.97	9.338%	$238.324	$238.32	$238.30	$238.30
Purchase #3	$177.71	10.672%	$196.6752	$196.68	$196.70	$196.70
Purchase #4	$72.40	12.554%	$81.4891	$81.49	$81.50	$81.50
Purchase #5	$193.37	5.762%	$204.512	$204.51	$204.50	$204.50
Purchase #6	$99.80	11.281%	$111.0584	$111.06	$111.05	$111.10
Purchase #7	$68.68	11.565%	$76.6228	$76.62	$76.60	$76.60
7 purchase totals =	$990.45		$1,083.3562	$1,083.35	$1,083.30	$1,083.40