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	$237.44	12.329%	$266.714	$266.71	$266.70	$266.70
Purchase #2	$12.54	9.607%	$13.7447	$13.74	$13.75	$13.70
Purchase #3	$225.78	6.451%	$240.3451	$240.35	$240.35	$240.30
Purchase #4	$67.52	7.258%	$72.4206	$72.42	$72.40	$72.40
Purchase #5	$114.58	11.654%	$127.9332	$127.93	$127.95	$127.90
Purchase #6	$248.28	10.353%	$273.9844	$273.98	$274.00	$274.00
Purchase #7	$81.86	5.583%	$86.4302	$86.43	$86.45	$86.40
7 purchase totals =	$988.00		$1,081.5722	$1,081.56	$1,081.60	$1,081.40