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	$111.59	5.592%	$117.8301	$117.83	$117.85	$117.80
Purchase #2	$153.25	10.234%	$168.9336	$168.93	$168.95	$168.90
Purchase #3	$122.90	7.464%	$132.0733	$132.07	$132.05	$132.10
Purchase #4	$62.25	7.820%	$67.118	$67.12	$67.10	$67.10
Purchase #5	$8.93	6.845%	$9.5413	$9.54	$9.55	$9.50
Purchase #6	$109.69	12.785%	$123.7139	$123.71	$123.70	$123.70
Purchase #7	$107.83	6.300%	$114.6233	$114.62	$114.60	$114.60
7 purchase totals =	$676.44		$733.8335	$733.82	$733.80	$733.70