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	$145.49	11.555%	$162.3014	$162.30	$162.30	$162.30
Purchase #2	$35.85	6.509%	$38.1835	$38.18	$38.20	$38.20
Purchase #3	$172.61	7.464%	$185.4936	$185.49	$185.50	$185.50
Purchase #4	$180.32	12.158%	$202.2433	$202.24	$202.25	$202.20
Purchase #5	$108.86	7.742%	$117.2879	$117.29	$117.30	$117.30
Purchase #6	$142.40	6.278%	$151.3399	$151.34	$151.35	$151.30
Purchase #7	$89.67	10.672%	$99.2396	$99.24	$99.25	$99.20
7 purchase totals =	$875.20		$956.0892	$956.08	$956.15	$956.00