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	$150.32	10.284%	$165.7789	$165.78	$165.80	$165.80
Purchase #2	$96.48	4.262%	$100.592	$100.59	$100.60	$100.60
Purchase #3	$168.37	7.657%	$181.2621	$181.26	$181.25	$181.30
Purchase #4	$200.67	7.225%	$215.1684	$215.17	$215.15	$215.20
Purchase #5	$224.70	7.534%	$241.6289	$241.63	$241.65	$241.60
Purchase #6	$97.29	3.462%	$100.6582	$100.66	$100.65	$100.70
Purchase #7	$182.87	11.467%	$203.8397	$203.84	$203.85	$203.80
7 purchase totals =	$1,120.70		$1,208.9282	$1,208.93	$1,208.95	$1,209.00