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	$32.68	7.871%	$35.2522	$35.25	$35.25	$35.30
Purchase #2	$152.90	5.257%	$160.938	$160.94	$160.95	$160.90
Purchase #3	$210.34	13.182%	$238.067	$238.07	$238.05	$238.10
Purchase #4	$56.31	12.870%	$63.5571	$63.56	$63.55	$63.60
Purchase #5	$114.86	10.144%	$126.5114	$126.51	$126.50	$126.50
Purchase #6	$126.81	6.239%	$134.7217	$134.72	$134.70	$134.70
Purchase #7	$105.41	5.858%	$111.5849	$111.58	$111.60	$111.60
7 purchase totals =	$799.31		$870.6323	$870.63	$870.60	$870.70