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	$179.63	13.618%	$204.092	$204.09	$204.10	$204.10
Purchase #2	$171.63	10.390%	$189.4624	$189.46	$189.45	$189.50
Purchase #3	$37.34	8.728%	$40.599	$40.60	$40.60	$40.60
Purchase #4	$91.90	12.272%	$103.178	$103.18	$103.20	$103.20
Purchase #5	$156.45	12.813%	$176.4959	$176.50	$176.50	$176.50
Purchase #6	$235.25	8.517%	$255.2862	$255.29	$255.30	$255.30
Purchase #7	$143.87	9.685%	$157.8038	$157.80	$157.80	$157.80
7 purchase totals =	$1,016.07		$1,126.9173	$1,126.92	$1,126.95	$1,127.00