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	$168.36	8.404%	$182.509	$182.51	$182.50	$182.50
Purchase #2	$38.70	5.591%	$40.8637	$40.86	$40.85	$40.90
Purchase #3	$141.88	9.630%	$155.543	$155.54	$155.55	$155.50
Purchase #4	$99.28	10.119%	$109.3261	$109.33	$109.35	$109.30
Purchase #5	$13.53	7.760%	$14.5799	$14.58	$14.60	$14.60
Purchase #6	$179.60	10.710%	$198.8352	$198.84	$198.85	$198.80
Purchase #7	$68.65	13.773%	$78.1052	$78.11	$78.10	$78.10
7 purchase totals =	$710.00		$779.7621	$779.77	$779.80	$779.70