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	$48.44	12.778%	$54.6297	$54.63	$54.65	$54.60
Purchase #2	$114.85	7.774%	$123.7784	$123.78	$123.80	$123.80
Purchase #3	$18.29	13.810%	$20.8158	$20.82	$20.80	$20.80
Purchase #4	$149.44	4.703%	$156.4682	$156.47	$156.45	$156.50
Purchase #5	$242.71	9.665%	$266.1679	$266.17	$266.15	$266.20
Purchase #6	$215.80	6.566%	$229.9694	$229.97	$229.95	$230.00
Purchase #7	$89.98	11.149%	$100.0119	$100.01	$100.00	$100.00
7 purchase totals =	$879.51		$951.8413	$951.85	$951.80	$951.90