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	$205.94	9.356%	$225.2077	$225.21	$225.20	$225.20
Purchase #2	$100.49	13.164%	$113.7185	$113.72	$113.70	$113.70
Purchase #3	$197.78	9.632%	$216.8302	$216.83	$216.85	$216.80
Purchase #4	$20.63	3.109%	$21.2714	$21.27	$21.25	$21.30
Purchase #5	$241.43	5.725%	$255.2519	$255.25	$255.25	$255.30
Purchase #6	$139.38	3.623%	$144.4297	$144.43	$144.45	$144.40
Purchase #7	$31.95	4.813%	$33.4878	$33.49	$33.50	$33.50
7 purchase totals =	$937.60		$1,010.1972	$1,010.20	$1,010.20	$1,010.20