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	$37.94	9.696%	$41.6187	$41.62	$41.60	$41.60
Purchase #2	$169.48	5.838%	$179.3742	$179.37	$179.35	$179.40
Purchase #3	$116.80	13.126%	$132.1312	$132.13	$132.15	$132.10
Purchase #4	$249.84	3.758%	$259.229	$259.23	$259.25	$259.20
Purchase #5	$36.76	10.209%	$40.5128	$40.51	$40.50	$40.50
Purchase #6	$180.98	8.676%	$196.6818	$196.68	$196.70	$196.70
Purchase #7	$141.90	12.683%	$159.8972	$159.90	$159.90	$159.90
7 purchase totals =	$933.70		$1,009.4449	$1,009.44	$1,009.45	$1,009.40