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	$105.62	11.326%	$117.5825	$117.58	$117.60	$117.60
Purchase #2	$18.81	5.746%	$19.8908	$19.89	$19.90	$19.90
Purchase #3	$97.68	11.674%	$109.0832	$109.08	$109.10	$109.10
Purchase #4	$227.77	4.854%	$238.826	$238.83	$238.85	$238.80
Purchase #5	$109.50	11.110%	$121.6655	$121.67	$121.65	$121.70
Purchase #6	$230.75	11.196%	$256.5848	$256.58	$256.60	$256.60
Purchase #7	$127.33	10.175%	$140.2858	$140.29	$140.30	$140.30
7 purchase totals =	$917.46		$1,003.9186	$1,003.92	$1,004.00	$1,004.00