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	$239.72	10.744%	$265.4755	$265.48	$265.50	$265.50
Purchase #2	$242.29	10.159%	$266.9042	$266.90	$266.90	$266.90
Purchase #3	$99.88	4.638%	$104.5124	$104.51	$104.50	$104.50
Purchase #4	$86.86	12.289%	$97.5342	$97.53	$97.55	$97.50
Purchase #5	$47.58	7.406%	$51.1038	$51.10	$51.10	$51.10
Purchase #6	$181.78	9.133%	$198.382	$198.38	$198.40	$198.40
Purchase #7	$71.82	10.564%	$79.4071	$79.41	$79.40	$79.40
7 purchase totals =	$969.93		$1,063.3192	$1,063.31	$1,063.35	$1,063.30