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	$169.87	6.510%	$180.9285	$180.93	$180.95	$180.90
Purchase #2	$139.78	13.367%	$158.4644	$158.46	$158.45	$158.50
Purchase #3	$135.91	5.303%	$143.1173	$143.12	$143.10	$143.10
Purchase #4	$102.38	10.207%	$112.8299	$112.83	$112.85	$112.80
Purchase #5	$164.51	9.403%	$179.9789	$179.98	$180.00	$180.00
Purchase #6	$164.53	11.564%	$183.5562	$183.56	$183.55	$183.60
Purchase #7	$136.35	12.274%	$153.0856	$153.09	$153.10	$153.10
7 purchase totals =	$1,013.33		$1,111.9608	$1,111.97	$1,112.00	$1,112.00