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	$128.41	12.813%	$144.8632	$144.86	$144.85	$144.90
Purchase #2	$216.50	10.712%	$239.6915	$239.69	$239.70	$239.70
Purchase #3	$118.42	4.410%	$123.6423	$123.64	$123.65	$123.60
Purchase #4	$158.46	9.859%	$174.0826	$174.08	$174.10	$174.10
Purchase #5	$34.34	12.658%	$38.6868	$38.69	$38.70	$38.70
Purchase #6	$145.32	7.596%	$156.3585	$156.36	$156.35	$156.40
Purchase #7	$211.79	3.244%	$218.6605	$218.66	$218.65	$218.70
7 purchase totals =	$1,013.24		$1,095.9854	$1,095.98	$1,096.00	$1,096.10