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	$195.63	8.788%	$212.822	$212.82	$212.80	$212.80
Purchase #2	$25.51	8.692%	$27.7273	$27.73	$27.75	$27.70
Purchase #3	$76.37	5.661%	$80.6933	$80.69	$80.70	$80.70
Purchase #4	$217.49	10.518%	$240.3656	$240.37	$240.35	$240.40
Purchase #5	$217.77	9.502%	$238.4625	$238.46	$238.45	$238.50
Purchase #6	$51.81	7.114%	$55.4958	$55.50	$55.50	$55.50
Purchase #7	$118.97	3.766%	$123.4504	$123.45	$123.45	$123.50
7 purchase totals =	$903.55		$979.0169	$979.02	$979.00	$979.10