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	$120.60	10.180%	$132.8771	$132.88	$132.90	$132.90
Purchase #2	$175.38	13.752%	$199.4983	$199.50	$199.50	$199.50
Purchase #3	$204.94	7.283%	$219.8658	$219.87	$219.85	$219.90
Purchase #4	$108.35	4.162%	$112.8595	$112.86	$112.85	$112.90
Purchase #5	$14.54	5.216%	$15.2984	$15.30	$15.30	$15.30
Purchase #6	$175.46	13.744%	$199.5752	$199.58	$199.60	$199.60
Purchase #7	$152.64	7.546%	$164.1582	$164.16	$164.15	$164.20
7 purchase totals =	$951.91		$1,044.1325	$1,044.15	$1,044.15	$1,044.30