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	$196.49	9.688%	$215.526	$215.53	$215.55	$215.50
Purchase #2	$99.78	3.559%	$103.3312	$103.33	$103.35	$103.30
Purchase #3	$188.88	10.335%	$208.4007	$208.40	$208.40	$208.40
Purchase #4	$134.26	10.302%	$148.0915	$148.09	$148.10	$148.10
Purchase #5	$186.60	9.554%	$204.4278	$204.43	$204.45	$204.40
Purchase #6	$147.71	11.766%	$165.0896	$165.09	$165.10	$165.10
Purchase #7	$55.32	9.603%	$60.6324	$60.63	$60.65	$60.60
7 purchase totals =	$1,009.04		$1,105.4992	$1,105.50	$1,105.60	$1,105.40