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	$54.51	8.308%	$59.0387	$59.04	$59.05	$59.00
Purchase #2	$64.47	9.276%	$70.4502	$70.45	$70.45	$70.50
Purchase #3	$239.87	8.171%	$259.4698	$259.47	$259.45	$259.50
Purchase #4	$90.98	3.871%	$94.5018	$94.50	$94.50	$94.50
Purchase #5	$10.80	10.353%	$11.9181	$11.92	$11.90	$11.90
Purchase #6	$62.42	5.861%	$66.0784	$66.08	$66.10	$66.10
Purchase #7	$243.88	5.215%	$256.5983	$256.60	$256.60	$256.60
7 purchase totals =	$766.93		$818.0553	$818.06	$818.05	$818.10