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	$47.61	10.420%	$52.571	$52.57	$52.55	$52.60
Purchase #2	$137.28	9.639%	$150.5124	$150.51	$150.50	$150.50
Purchase #3	$160.55	7.423%	$172.4676	$172.47	$172.45	$172.50
Purchase #4	$25.98	13.657%	$29.5281	$29.53	$29.55	$29.50
Purchase #5	$200.41	9.361%	$219.1704	$219.17	$219.15	$219.20
Purchase #6	$217.95	5.800%	$230.5911	$230.59	$230.60	$230.60
Purchase #7	$49.31	12.269%	$55.3598	$55.36	$55.35	$55.40
7 purchase totals =	$839.09		$910.2004	$910.20	$910.15	$910.30