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	$224.51	10.266%	$247.5582	$247.56	$247.55	$247.60
Purchase #2	$198.54	4.853%	$208.1751	$208.18	$208.20	$208.20
Purchase #3	$53.37	11.661%	$59.5935	$59.59	$59.60	$59.60
Purchase #4	$40.64	9.321%	$44.4281	$44.43	$44.45	$44.40
Purchase #5	$72.63	11.273%	$80.8176	$80.82	$80.80	$80.80
Purchase #6	$235.63	8.307%	$255.2038	$255.20	$255.20	$255.20
Purchase #7	$34.44	9.175%	$37.5999	$37.60	$37.60	$37.60
7 purchase totals =	$859.76		$933.3762	$933.38	$933.40	$933.40