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	$146.45	6.862%	$156.4994	$156.50	$156.50	$156.50
Purchase #2	$242.60	5.706%	$256.4428	$256.44	$256.45	$256.40
Purchase #3	$72.63	13.270%	$82.268	$82.27	$82.25	$82.30
Purchase #4	$207.86	6.294%	$220.9427	$220.94	$220.95	$220.90
Purchase #5	$179.77	4.476%	$187.8165	$187.82	$187.80	$187.80
Purchase #6	$11.82	6.197%	$12.5525	$12.55	$12.55	$12.60
Purchase #7	$242.79	10.587%	$268.4942	$268.49	$268.50	$268.50
7 purchase totals =	$1,103.92		$1,185.0161	$1,185.01	$1,185.00	$1,185.00