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	$160.35	10.116%	$176.571	$176.57	$176.55	$176.60
Purchase #2	$83.92	6.761%	$89.5938	$89.59	$89.60	$89.60
Purchase #3	$35.87	10.375%	$39.5915	$39.59	$39.60	$39.60
Purchase #4	$48.56	9.275%	$53.0639	$53.06	$53.05	$53.10
Purchase #5	$7.82	4.419%	$8.1656	$8.17	$8.15	$8.20
Purchase #6	$153.68	12.526%	$172.93	$172.93	$172.95	$172.90
Purchase #7	$202.83	11.396%	$225.9445	$225.94	$225.95	$225.90
7 purchase totals =	$693.03		$765.8603	$765.85	$765.85	$765.90