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	$182.58	10.565%	$201.8696	$201.87	$201.85	$201.90
Purchase #2	$46.99	9.623%	$51.5118	$51.51	$51.50	$51.50
Purchase #3	$23.51	5.446%	$24.7904	$24.79	$24.80	$24.80
Purchase #4	$41.70	5.338%	$43.9259	$43.93	$43.95	$43.90
Purchase #5	$107.87	3.322%	$111.4534	$111.45	$111.45	$111.50
Purchase #6	$85.37	5.780%	$90.3044	$90.30	$90.30	$90.30
Purchase #7	$127.43	9.311%	$139.295	$139.30	$139.30	$139.30
7 purchase totals =	$615.45		$663.1505	$663.15	$663.15	$663.20