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	$100.83	4.725%	$105.5942	$105.59	$105.60	$105.60
Purchase #2	$72.32	13.609%	$82.162	$82.16	$82.15	$82.20
Purchase #3	$179.71	4.615%	$188.0036	$188.00	$188.00	$188.00
Purchase #4	$103.95	7.176%	$111.4095	$111.41	$111.40	$111.40
Purchase #5	$68.78	12.189%	$77.1636	$77.16	$77.15	$77.20
Purchase #6	$41.62	11.673%	$46.4783	$46.48	$46.50	$46.50
Purchase #7	$150.59	8.506%	$163.3992	$163.40	$163.40	$163.40
7 purchase totals =	$717.80		$774.2104	$774.20	$774.20	$774.30