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	$145.54	9.109%	$158.7972	$158.80	$158.80	$158.80
Purchase #2	$37.96	10.334%	$41.8828	$41.88	$41.90	$41.90
Purchase #3	$131.35	3.684%	$136.1889	$136.19	$136.20	$136.20
Purchase #4	$90.95	3.250%	$93.9059	$93.91	$93.90	$93.90
Purchase #5	$168.75	13.716%	$191.8958	$191.90	$191.90	$191.90
Purchase #6	$241.54	6.162%	$256.4237	$256.42	$256.40	$256.40
Purchase #7	$119.69	10.341%	$132.0671	$132.07	$132.05	$132.10
7 purchase totals =	$935.78		$1,011.1614	$1,011.17	$1,011.15	$1,011.20