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	$164.62	11.451%	$183.4706	$183.47	$183.45	$183.50
Purchase #2	$224.34	4.670%	$234.8167	$234.82	$234.80	$234.80
Purchase #3	$148.89	11.638%	$166.2178	$166.22	$166.20	$166.20
Purchase #4	$94.70	6.644%	$100.9919	$100.99	$101.00	$101.00
Purchase #5	$19.44	10.421%	$21.4658	$21.47	$21.45	$21.50
Purchase #6	$153.73	8.559%	$166.8878	$166.89	$166.90	$166.90
Purchase #7	$124.73	3.230%	$128.7588	$128.76	$128.75	$128.80
7 purchase totals =	$930.45		$1,002.6094	$1,002.62	$1,002.55	$1,002.70