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	$209.26	8.409%	$226.8567	$226.86	$226.85	$226.90
Purchase #2	$119.83	9.291%	$130.9634	$130.96	$130.95	$131.00
Purchase #3	$107.75	3.339%	$111.3478	$111.35	$111.35	$111.30
Purchase #4	$134.84	9.275%	$147.3464	$147.35	$147.35	$147.30
Purchase #5	$101.72	9.342%	$111.2227	$111.22	$111.20	$111.20
Purchase #6	$241.86	5.561%	$255.3098	$255.31	$255.30	$255.30
Purchase #7	$12.74	10.571%	$14.0867	$14.09	$14.10	$14.10
7 purchase totals =	$928.00		$997.1335	$997.14	$997.10	$997.10