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	$49.32	5.719%	$52.1406	$52.14	$52.15	$52.10
Purchase #2	$157.38	9.420%	$172.2052	$172.21	$172.20	$172.20
Purchase #3	$14.64	8.139%	$15.8315	$15.83	$15.85	$15.80
Purchase #4	$114.60	7.679%	$123.4001	$123.40	$123.40	$123.40
Purchase #5	$100.41	4.510%	$104.9385	$104.94	$104.95	$104.90
Purchase #6	$229.67	5.427%	$242.1342	$242.13	$242.15	$242.10
Purchase #7	$196.87	10.425%	$217.3937	$217.39	$217.40	$217.40
7 purchase totals =	$862.89		$928.0438	$928.04	$928.10	$927.90