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	$108.86	5.436%	$114.7776	$114.78	$114.80	$114.80
Purchase #2	$171.47	3.713%	$177.8367	$177.84	$177.85	$177.80
Purchase #3	$18.77	9.345%	$20.5241	$20.52	$20.50	$20.50
Purchase #4	$212.57	11.684%	$237.4067	$237.41	$237.40	$237.40
Purchase #5	$191.55	4.319%	$199.823	$199.82	$199.80	$199.80
Purchase #6	$175.29	9.301%	$191.5937	$191.59	$191.60	$191.60
Purchase #7	$70.59	9.632%	$77.3892	$77.39	$77.40	$77.40
7 purchase totals =	$949.10		$1,019.3510	$1,019.35	$1,019.35	$1,019.30