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	$194.59	7.791%	$209.7505	$209.75	$209.75	$209.80
Purchase #2	$166.70	10.605%	$184.3785	$184.38	$184.40	$184.40
Purchase #3	$152.89	12.237%	$171.5991	$171.60	$171.60	$171.60
Purchase #4	$169.35	12.210%	$190.0276	$190.03	$190.05	$190.00
Purchase #5	$194.50	10.755%	$215.4185	$215.42	$215.40	$215.40
Purchase #6	$225.40	6.274%	$239.5416	$239.54	$239.55	$239.50
Purchase #7	$46.52	3.401%	$48.1021	$48.10	$48.10	$48.10
7 purchase totals =	$1,149.95		$1,258.8179	$1,258.82	$1,258.85	$1,258.80