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	$151.90	6.795%	$162.2216	$162.22	$162.20	$162.20
Purchase #2	$18.60	10.728%	$20.5954	$20.60	$20.60	$20.60
Purchase #3	$66.96	3.156%	$69.0733	$69.07	$69.05	$69.10
Purchase #4	$116.68	5.564%	$123.1721	$123.17	$123.15	$123.20
Purchase #5	$160.48	11.516%	$178.9609	$178.96	$178.95	$179.00
Purchase #6	$129.48	10.613%	$143.2217	$143.22	$143.20	$143.20
Purchase #7	$36.60	12.368%	$41.1267	$41.13	$41.15	$41.10
7 purchase totals =	$680.70		$738.3717	$738.37	$738.30	$738.40