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	$12.93	9.597%	$14.1709	$14.17	$14.15	$14.20
Purchase #2	$198.28	12.738%	$223.5369	$223.54	$223.55	$223.50
Purchase #3	$49.57	9.482%	$54.2702	$54.27	$54.25	$54.30
Purchase #4	$28.28	11.770%	$31.6086	$31.61	$31.60	$31.60
Purchase #5	$12.95	8.296%	$14.0243	$14.02	$14.00	$14.00
Purchase #6	$39.51	3.575%	$40.9225	$40.92	$40.90	$40.90
Purchase #7	$230.31	9.835%	$252.961	$252.96	$252.95	$253.00
7 purchase totals =	$571.83		$631.4944	$631.49	$631.40	$631.50