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	$165.61	13.405%	$187.81	$187.81	$187.80	$187.80
Purchase #2	$166.75	10.520%	$184.2921	$184.29	$184.30	$184.30
Purchase #3	$217.42	6.251%	$231.0109	$231.01	$231.00	$231.00
Purchase #4	$187.36	9.156%	$204.5147	$204.51	$204.50	$204.50
Purchase #5	$46.83	3.293%	$48.3721	$48.37	$48.35	$48.40
Purchase #6	$88.40	12.726%	$99.6498	$99.65	$99.65	$99.60
Purchase #7	$95.83	4.787%	$100.4174	$100.42	$100.40	$100.40
7 purchase totals =	$968.20		$1,056.0670	$1,056.06	$1,056.00	$1,056.00