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	$26.68	9.660%	$29.2573	$29.26	$29.25	$29.30
Purchase #2	$114.29	11.445%	$127.3705	$127.37	$127.35	$127.40
Purchase #3	$31.28	5.796%	$33.093	$33.09	$33.10	$33.10
Purchase #4	$28.36	11.309%	$31.5672	$31.57	$31.55	$31.60
Purchase #5	$248.47	3.210%	$256.4459	$256.45	$256.45	$256.40
Purchase #6	$75.32	10.440%	$83.1834	$83.18	$83.20	$83.20
Purchase #7	$102.98	10.825%	$114.1276	$114.13	$114.15	$114.10
7 purchase totals =	$627.38		$675.0449	$675.05	$675.05	$675.10