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	$216.48	7.780%	$233.3221	$233.32	$233.30	$233.30
Purchase #2	$161.83	6.688%	$172.6532	$172.65	$172.65	$172.70
Purchase #3	$160.55	7.820%	$173.105	$173.11	$173.10	$173.10
Purchase #4	$15.48	11.460%	$17.254	$17.25	$17.25	$17.30
Purchase #5	$215.40	3.491%	$222.9196	$222.92	$222.90	$222.90
Purchase #6	$61.50	5.699%	$65.0049	$65.00	$65.00	$65.00
Purchase #7	$69.91	3.409%	$72.2932	$72.29	$72.30	$72.30
7 purchase totals =	$901.15		$956.5520	$956.54	$956.50	$956.60