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	$241.59	6.215%	$256.6048	$256.60	$256.60	$256.60
Purchase #2	$189.69	4.702%	$198.6092	$198.61	$198.60	$198.60
Purchase #3	$215.58	13.106%	$243.8339	$243.83	$243.85	$243.80
Purchase #4	$156.86	10.141%	$172.7672	$172.77	$172.75	$172.80
Purchase #5	$150.44	8.333%	$162.9762	$162.98	$163.00	$163.00
Purchase #6	$250.42	4.721%	$262.2423	$262.24	$262.25	$262.20
Purchase #7	$128.65	5.866%	$136.1966	$136.20	$136.20	$136.20
7 purchase totals =	$1,333.23		$1,433.2302	$1,433.23	$1,433.25	$1,433.20