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	$12.86	12.808%	$14.5071	$14.51	$14.50	$14.50
Purchase #2	$201.78	10.474%	$222.9144	$222.91	$222.90	$222.90
Purchase #3	$125.90	7.850%	$135.7832	$135.78	$135.80	$135.80
Purchase #4	$172.52	12.850%	$194.6888	$194.69	$194.70	$194.70
Purchase #5	$14.32	11.617%	$15.9836	$15.98	$16.00	$16.00
Purchase #6	$237.72	5.548%	$250.9087	$250.91	$250.90	$250.90
Purchase #7	$151.83	13.333%	$172.0735	$172.07	$172.05	$172.10
7 purchase totals =	$916.93		$1,006.8593	$1,006.85	$1,006.85	$1,006.90