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	$105.70	7.286%	$113.4013	$113.40	$113.40	$113.40
Purchase #2	$123.29	6.699%	$131.5492	$131.55	$131.55	$131.50
Purchase #3	$92.33	12.473%	$103.8463	$103.85	$103.85	$103.80
Purchase #4	$17.34	7.192%	$18.5871	$18.59	$18.60	$18.60
Purchase #5	$210.88	6.296%	$224.157	$224.16	$224.15	$224.20
Purchase #6	$153.46	7.422%	$164.8498	$164.85	$164.85	$164.80
Purchase #7	$179.78	4.204%	$187.338	$187.34	$187.35	$187.30
7 purchase totals =	$882.78		$943.7287	$943.74	$943.75	$943.60