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	$169.97	10.858%	$188.4253	$188.43	$188.45	$188.40
Purchase #2	$212.94	12.469%	$239.4915	$239.49	$239.50	$239.50
Purchase #3	$61.33	9.874%	$67.3857	$67.39	$67.40	$67.40
Purchase #4	$68.88	13.691%	$78.3104	$78.31	$78.30	$78.30
Purchase #5	$75.83	13.156%	$85.8062	$85.81	$85.80	$85.80
Purchase #6	$115.85	5.359%	$122.0584	$122.06	$122.05	$122.10
Purchase #7	$212.69	13.696%	$241.82	$241.82	$241.80	$241.80
7 purchase totals =	$917.49		$1,023.2975	$1,023.31	$1,023.30	$1,023.30