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	$244.30	4.482%	$255.2495	$255.25	$255.25	$255.20
Purchase #2	$200.38	8.130%	$216.6709	$216.67	$216.65	$216.70
Purchase #3	$47.54	10.497%	$52.5303	$52.53	$52.55	$52.50
Purchase #4	$109.35	3.124%	$112.7661	$112.77	$112.75	$112.80
Purchase #5	$178.60	5.746%	$188.8624	$188.86	$188.85	$188.90
Purchase #6	$14.56	6.682%	$15.5329	$15.53	$15.55	$15.50
Purchase #7	$244.42	6.152%	$259.4567	$259.46	$259.45	$259.50
7 purchase totals =	$1,039.15		$1,101.0688	$1,101.07	$1,101.05	$1,101.10