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	$67.36	9.641%	$73.8542	$73.85	$73.85	$73.90
Purchase #2	$37.33	4.388%	$38.968	$38.97	$38.95	$39.00
Purchase #3	$38.96	9.725%	$42.7489	$42.75	$42.75	$42.70
Purchase #4	$48.63	11.714%	$54.3265	$54.33	$54.35	$54.30
Purchase #5	$51.78	5.806%	$54.7863	$54.79	$54.80	$54.80
Purchase #6	$71.76	10.674%	$79.4197	$79.42	$79.40	$79.40
Purchase #7	$124.85	13.591%	$141.8184	$141.82	$141.80	$141.80
7 purchase totals =	$440.67		$485.9220	$485.93	$485.90	$485.90