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	$189.49	7.850%	$204.365	$204.37	$204.35	$204.40
Purchase #2	$100.37	12.105%	$112.5198	$112.52	$112.50	$112.50
Purchase #3	$104.47	7.643%	$112.4546	$112.45	$112.45	$112.50
Purchase #4	$154.53	9.644%	$169.4329	$169.43	$169.45	$169.40
Purchase #5	$179.41	4.198%	$186.9416	$186.94	$186.95	$186.90
Purchase #6	$60.27	3.211%	$62.2053	$62.21	$62.20	$62.20
Purchase #7	$72.98	8.167%	$78.9403	$78.94	$78.95	$78.90
7 purchase totals =	$861.52		$926.8595	$926.86	$926.85	$926.80