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	$208.62	10.865%	$231.2866	$231.29	$231.30	$231.30
Purchase #2	$208.82	4.387%	$217.9809	$217.98	$218.00	$218.00
Purchase #3	$203.45	7.170%	$218.0374	$218.04	$218.05	$218.00
Purchase #4	$139.65	7.312%	$149.8612	$149.86	$149.85	$149.90
Purchase #5	$81.86	5.811%	$86.6169	$86.62	$86.60	$86.60
Purchase #6	$87.50	4.194%	$91.1698	$91.17	$91.15	$91.20
Purchase #7	$40.65	11.860%	$45.4711	$45.47	$45.45	$45.50
7 purchase totals =	$970.55		$1,040.4239	$1,040.43	$1,040.40	$1,040.50