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	$104.69	4.470%	$109.3696	$109.37	$109.35	$109.40
Purchase #2	$104.72	13.803%	$119.1745	$119.17	$119.15	$119.20
Purchase #3	$239.54	3.295%	$247.4328	$247.43	$247.45	$247.40
Purchase #4	$125.78	8.377%	$136.3166	$136.32	$136.30	$136.30
Purchase #5	$38.35	8.105%	$41.4583	$41.46	$41.45	$41.50
Purchase #6	$43.96	12.857%	$49.6119	$49.61	$49.60	$49.60
Purchase #7	$74.91	11.469%	$83.5014	$83.50	$83.50	$83.50
7 purchase totals =	$731.95		$786.8651	$786.86	$786.80	$786.90