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	$61.26	5.606%	$64.6942	$64.69	$64.70	$64.70
Purchase #2	$67.89	7.318%	$72.8582	$72.86	$72.85	$72.90
Purchase #3	$111.97	13.727%	$127.3401	$127.34	$127.35	$127.30
Purchase #4	$198.69	7.714%	$214.0169	$214.02	$214.00	$214.00
Purchase #5	$194.83	10.836%	$215.9418	$215.94	$215.95	$215.90
Purchase #6	$161.94	13.591%	$183.9493	$183.95	$183.95	$183.90
Purchase #7	$34.45	11.871%	$38.5396	$38.54	$38.55	$38.50
7 purchase totals =	$831.03		$917.3401	$917.34	$917.35	$917.20