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	$98.73	10.615%	$109.2102	$109.21	$109.20	$109.20
Purchase #2	$124.73	13.380%	$141.4189	$141.42	$141.40	$141.40
Purchase #3	$200.58	12.832%	$226.3184	$226.32	$226.30	$226.30
Purchase #4	$105.39	10.639%	$116.6024	$116.60	$116.60	$116.60
Purchase #5	$37.59	8.431%	$40.7592	$40.76	$40.75	$40.80
Purchase #6	$54.94	13.853%	$62.5508	$62.55	$62.55	$62.60
Purchase #7	$134.91	8.595%	$146.5055	$146.51	$146.50	$146.50
7 purchase totals =	$756.87		$843.3654	$843.37	$843.30	$843.40