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	$37.68	12.535%	$42.4032	$42.40	$42.40	$42.40
Purchase #2	$7.27	4.483%	$7.5959	$7.60	$7.60	$7.60
Purchase #3	$134.69	5.461%	$142.0454	$142.05	$142.05	$142.00
Purchase #4	$170.98	4.681%	$178.9836	$178.98	$179.00	$179.00
Purchase #5	$50.81	8.827%	$55.295	$55.30	$55.30	$55.30
Purchase #6	$58.78	5.615%	$62.0805	$62.08	$62.10	$62.10
Purchase #7	$198.83	13.643%	$225.9564	$225.96	$225.95	$226.00
7 purchase totals =	$659.04		$714.3600	$714.37	$714.40	$714.40