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	$10.75	11.627%	$11.9999	$12.00	$12.00	$12.00
Purchase #2	$210.86	5.454%	$222.3603	$222.36	$222.35	$222.40
Purchase #3	$155.54	5.763%	$164.5038	$164.50	$164.50	$164.50
Purchase #4	$79.99	5.763%	$84.5998	$84.60	$84.60	$84.60
Purchase #5	$192.68	6.573%	$205.3449	$205.34	$205.35	$205.30
Purchase #6	$220.90	5.852%	$233.8271	$233.83	$233.85	$233.80
Purchase #7	$196.81	11.740%	$219.9155	$219.92	$219.90	$219.90
7 purchase totals =	$1,067.53		$1,142.5513	$1,142.55	$1,142.55	$1,142.50