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	$214.47	4.667%	$224.4793	$224.48	$224.50	$224.50
Purchase #2	$149.60	3.195%	$154.3797	$154.38	$154.40	$154.40
Purchase #3	$190.61	8.142%	$206.1295	$206.13	$206.15	$206.10
Purchase #4	$246.43	5.444%	$259.8456	$259.85	$259.85	$259.80
Purchase #5	$156.42	5.393%	$164.8557	$164.86	$164.85	$164.90
Purchase #6	$9.95	11.301%	$11.0744	$11.07	$11.05	$11.10
Purchase #7	$36.51	12.511%	$41.0778	$41.08	$41.10	$41.10
7 purchase totals =	$1,003.99		$1,061.8420	$1,061.85	$1,061.90	$1,061.90