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	$114.38	8.198%	$123.7569	$123.76	$123.75	$123.80
Purchase #2	$52.39	10.567%	$57.9261	$57.93	$57.95	$57.90
Purchase #3	$214.90	10.783%	$238.0727	$238.07	$238.05	$238.10
Purchase #4	$229.26	11.792%	$256.2943	$256.29	$256.30	$256.30
Purchase #5	$30.87	11.204%	$34.3287	$34.33	$34.35	$34.30
Purchase #6	$241.40	10.198%	$266.018	$266.02	$266.00	$266.00
Purchase #7	$62.62	5.556%	$66.0992	$66.10	$66.10	$66.10
7 purchase totals =	$945.82		$1,042.4959	$1,042.50	$1,042.50	$1,042.50