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	$209.38	13.762%	$238.1949	$238.19	$238.20	$238.20
Purchase #2	$237.86	3.326%	$245.7712	$245.77	$245.75	$245.80
Purchase #3	$225.60	5.641%	$238.3261	$238.33	$238.35	$238.30
Purchase #4	$53.32	6.734%	$56.9106	$56.91	$56.90	$56.90
Purchase #5	$237.85	9.341%	$260.0676	$260.07	$260.05	$260.10
Purchase #6	$18.82	6.855%	$20.1101	$20.11	$20.10	$20.10
Purchase #7	$19.35	10.226%	$21.3287	$21.33	$21.35	$21.30
7 purchase totals =	$1,002.18		$1,080.7092	$1,080.71	$1,080.70	$1,080.70