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	$34.94	10.330%	$38.5493	$38.55	$38.55	$38.50
Purchase #2	$56.43	11.154%	$62.7242	$62.72	$62.70	$62.70
Purchase #3	$177.37	10.692%	$196.3344	$196.33	$196.35	$196.30
Purchase #4	$220.38	13.533%	$250.204	$250.20	$250.20	$250.20
Purchase #5	$244.97	11.239%	$272.5022	$272.50	$272.50	$272.50
Purchase #6	$46.41	3.475%	$48.0227	$48.02	$48.00	$48.00
Purchase #7	$147.36	11.347%	$164.0809	$164.08	$164.10	$164.10
7 purchase totals =	$927.86		$1,032.4177	$1,032.40	$1,032.40	$1,032.30