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	$39.39	11.498%	$43.9191	$43.92	$43.90	$43.90
Purchase #2	$159.42	3.870%	$165.5896	$165.59	$165.60	$165.60
Purchase #3	$219.68	10.152%	$241.9819	$241.98	$242.00	$242.00
Purchase #4	$111.48	11.609%	$124.4217	$124.42	$124.40	$124.40
Purchase #5	$95.75	5.635%	$101.1455	$101.15	$101.15	$101.10
Purchase #6	$197.55	7.444%	$212.2556	$212.26	$212.25	$212.30
Purchase #7	$144.97	9.359%	$158.5377	$158.54	$158.55	$158.50
7 purchase totals =	$968.24		$1,047.8511	$1,047.86	$1,047.85	$1,047.80