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	$149.42	11.698%	$166.8992	$166.90	$166.90	$166.90
Purchase #2	$41.90	12.365%	$47.0809	$47.08	$47.10	$47.10
Purchase #3	$144.62	13.656%	$164.3693	$164.37	$164.35	$164.40
Purchase #4	$213.94	4.586%	$223.7513	$223.75	$223.75	$223.80
Purchase #5	$198.62	5.532%	$209.6077	$209.61	$209.60	$209.60
Purchase #6	$215.28	12.393%	$241.9597	$241.96	$241.95	$242.00
Purchase #7	$99.72	12.197%	$111.8828	$111.88	$111.90	$111.90
7 purchase totals =	$1,063.50		$1,165.5509	$1,165.55	$1,165.55	$1,165.70