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	$84.28	4.202%	$87.8214	$87.82	$87.80	$87.80
Purchase #2	$9.33	13.496%	$10.5892	$10.59	$10.60	$10.60
Purchase #3	$136.34	8.779%	$148.3093	$148.31	$148.30	$148.30
Purchase #4	$132.43	13.850%	$150.7716	$150.77	$150.75	$150.80
Purchase #5	$103.38	8.236%	$111.8944	$111.89	$111.90	$111.90
Purchase #6	$21.83	10.258%	$24.0693	$24.07	$24.05	$24.10
Purchase #7	$90.31	9.371%	$98.773	$98.77	$98.75	$98.80
7 purchase totals =	$577.90		$632.2282	$632.22	$632.15	$632.30