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	$40.66	9.425%	$44.4922	$44.49	$44.50	$44.50
Purchase #2	$56.57	11.259%	$62.9392	$62.94	$62.95	$62.90
Purchase #3	$205.34	6.597%	$218.8863	$218.89	$218.90	$218.90
Purchase #4	$240.43	4.577%	$251.4345	$251.43	$251.45	$251.40
Purchase #5	$41.89	7.719%	$45.1235	$45.12	$45.10	$45.10
Purchase #6	$125.62	9.543%	$137.6079	$137.61	$137.60	$137.60
Purchase #7	$225.42	9.333%	$246.4584	$246.46	$246.45	$246.50
7 purchase totals =	$935.93		$1,006.9420	$1,006.94	$1,006.95	$1,006.90