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	$171.60	10.660%	$189.8926	$189.89	$189.90	$189.90
Purchase #2	$226.93	7.476%	$243.8953	$243.90	$243.90	$243.90
Purchase #3	$10.30	7.575%	$11.0802	$11.08	$11.10	$11.10
Purchase #4	$142.93	12.338%	$160.5647	$160.56	$160.55	$160.60
Purchase #5	$231.56	10.724%	$256.3925	$256.39	$256.40	$256.40
Purchase #6	$12.94	11.217%	$14.3915	$14.39	$14.40	$14.40
Purchase #7	$250.83	5.616%	$264.9166	$264.92	$264.90	$264.90
7 purchase totals =	$1,047.09		$1,141.1334	$1,141.13	$1,141.15	$1,141.20