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	$95.35	10.166%	$105.0433	$105.04	$105.05	$105.00
Purchase #2	$248.52	6.264%	$264.0873	$264.09	$264.10	$264.10
Purchase #3	$96.47	9.380%	$105.5189	$105.52	$105.50	$105.50
Purchase #4	$56.38	11.719%	$62.9872	$62.99	$63.00	$63.00
Purchase #5	$95.84	12.654%	$107.9676	$107.97	$107.95	$108.00
Purchase #6	$204.94	11.290%	$228.0777	$228.08	$228.10	$228.10
Purchase #7	$163.26	11.404%	$181.8782	$181.88	$181.90	$181.90
7 purchase totals =	$960.76		$1,055.5602	$1,055.57	$1,055.60	$1,055.60