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	$82.35	12.449%	$92.6018	$92.60	$92.60	$92.60
Purchase #2	$225.55	13.704%	$256.4594	$256.46	$256.45	$256.50
Purchase #3	$184.86	11.206%	$205.5754	$205.58	$205.60	$205.60
Purchase #4	$134.72	3.225%	$139.0647	$139.06	$139.05	$139.10
Purchase #5	$188.71	3.110%	$194.5789	$194.58	$194.60	$194.60
Purchase #6	$21.85	13.759%	$24.8563	$24.86	$24.85	$24.90
Purchase #7	$170.94	3.276%	$176.54	$176.54	$176.55	$176.50
7 purchase totals =	$1,008.98		$1,089.6765	$1,089.68	$1,089.70	$1,089.80