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	$105.71	5.356%	$111.3718	$111.37	$111.35	$111.40
Purchase #2	$182.97	9.537%	$200.4198	$200.42	$200.40	$200.40
Purchase #3	$69.37	12.233%	$77.856	$77.86	$77.85	$77.90
Purchase #4	$148.90	7.850%	$160.5887	$160.59	$160.60	$160.60
Purchase #5	$191.95	4.734%	$201.0369	$201.04	$201.05	$201.00
Purchase #6	$104.98	7.169%	$112.506	$112.51	$112.50	$112.50
Purchase #7	$245.55	13.785%	$279.3991	$279.40	$279.40	$279.40
7 purchase totals =	$1,049.43		$1,143.1783	$1,143.19	$1,143.15	$1,143.20