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	$214.72	13.641%	$244.01	$244.01	$244.00	$244.00
Purchase #2	$116.53	6.823%	$124.4808	$124.48	$124.50	$124.50
Purchase #3	$242.55	8.380%	$262.8757	$262.88	$262.90	$262.90
Purchase #4	$100.68	12.261%	$113.0244	$113.02	$113.00	$113.00
Purchase #5	$128.66	8.535%	$139.6411	$139.64	$139.65	$139.60
Purchase #6	$158.87	5.385%	$167.4251	$167.43	$167.45	$167.40
Purchase #7	$45.59	7.188%	$48.867	$48.87	$48.85	$48.90
7 purchase totals =	$1,007.60		$1,100.3241	$1,100.33	$1,100.35	$1,100.30