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	$101.69	4.360%	$106.1237	$106.12	$106.10	$106.10
Purchase #2	$212.33	3.798%	$220.3943	$220.39	$220.40	$220.40
Purchase #3	$41.26	5.327%	$43.4579	$43.46	$43.45	$43.50
Purchase #4	$102.58	9.178%	$111.9948	$111.99	$112.00	$112.00
Purchase #5	$240.53	12.434%	$270.4375	$270.44	$270.45	$270.40
Purchase #6	$81.39	9.750%	$89.3255	$89.33	$89.35	$89.30
Purchase #7	$199.78	12.789%	$225.3299	$225.33	$225.35	$225.30
7 purchase totals =	$979.56		$1,067.0636	$1,067.06	$1,067.10	$1,067.00