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	$213.62	4.772%	$223.8139	$223.81	$223.80	$223.80
Purchase #2	$65.28	5.728%	$69.0192	$69.02	$69.00	$69.00
Purchase #3	$193.60	3.327%	$200.0411	$200.04	$200.05	$200.00
Purchase #4	$238.81	3.226%	$246.514	$246.51	$246.50	$246.50
Purchase #5	$79.28	13.561%	$90.0312	$90.03	$90.05	$90.00
Purchase #6	$224.32	12.571%	$252.5193	$252.52	$252.50	$252.50
Purchase #7	$90.98	13.527%	$103.2869	$103.29	$103.30	$103.30
7 purchase totals =	$1,105.89		$1,185.2256	$1,185.22	$1,185.20	$1,185.10