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	$127.58	12.649%	$143.7176	$143.72	$143.70	$143.70
Purchase #2	$41.25	7.686%	$44.4205	$44.42	$44.40	$44.40
Purchase #3	$29.51	10.277%	$32.5427	$32.54	$32.55	$32.50
Purchase #4	$246.53	3.683%	$255.6097	$255.61	$255.60	$255.60
Purchase #5	$45.46	8.515%	$49.3309	$49.33	$49.35	$49.30
Purchase #6	$134.84	10.188%	$148.5775	$148.58	$148.60	$148.60
Purchase #7	$226.35	6.586%	$241.2574	$241.26	$241.25	$241.30
7 purchase totals =	$851.52		$915.4563	$915.46	$915.45	$915.40