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	$39.69	10.453%	$43.8388	$43.84	$43.85	$43.80
Purchase #2	$91.38	12.747%	$103.0282	$103.03	$103.05	$103.00
Purchase #3	$102.96	13.569%	$116.9306	$116.93	$116.95	$116.90
Purchase #4	$40.88	5.228%	$43.0172	$43.02	$43.00	$43.00
Purchase #5	$21.68	7.843%	$23.3804	$23.38	$23.40	$23.40
Purchase #6	$102.32	11.168%	$113.7471	$113.75	$113.75	$113.70
Purchase #7	$155.57	10.798%	$172.3684	$172.37	$172.35	$172.40
7 purchase totals =	$554.48		$616.3107	$616.32	$616.35	$616.20