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	$39.36	13.235%	$44.5693	$44.57	$44.55	$44.60
Purchase #2	$134.76	4.816%	$141.25	$141.25	$141.25	$141.30
Purchase #3	$46.94	4.314%	$48.965	$48.97	$48.95	$49.00
Purchase #4	$13.92	13.114%	$15.7455	$15.75	$15.75	$15.70
Purchase #5	$66.48	7.233%	$71.2885	$71.29	$71.30	$71.30
Purchase #6	$13.41	5.397%	$14.1337	$14.13	$14.15	$14.10
Purchase #7	$182.63	7.366%	$196.0825	$196.08	$196.10	$196.10
7 purchase totals =	$497.50		$532.0345	$532.04	$532.05	$532.10