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	$5.60	11.583%	$6.2486	$6.25	$6.25	$6.20
Purchase #2	$210.32	13.197%	$238.0759	$238.08	$238.10	$238.10
Purchase #3	$72.70	8.415%	$78.8177	$78.82	$78.80	$78.80
Purchase #4	$132.82	8.425%	$144.0101	$144.01	$144.00	$144.00
Purchase #5	$54.35	12.510%	$61.1492	$61.15	$61.15	$61.10
Purchase #6	$22.98	9.277%	$25.1119	$25.11	$25.10	$25.10
Purchase #7	$155.65	10.552%	$172.0742	$172.07	$172.05	$172.10
7 purchase totals =	$654.42		$725.4876	$725.49	$725.45	$725.40