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	$236.43	13.683%	$268.7807	$268.78	$268.80	$268.80
Purchase #2	$212.62	4.544%	$222.2815	$222.28	$222.30	$222.30
Purchase #3	$52.66	4.154%	$54.8475	$54.85	$54.85	$54.80
Purchase #4	$139.66	10.257%	$153.9849	$153.98	$154.00	$154.00
Purchase #5	$248.37	13.296%	$281.3933	$281.39	$281.40	$281.40
Purchase #6	$108.78	7.363%	$116.7895	$116.79	$116.80	$116.80
Purchase #7	$47.85	13.581%	$54.3485	$54.35	$54.35	$54.30
7 purchase totals =	$1,046.37		$1,152.4259	$1,152.42	$1,152.50	$1,152.40