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	$38.59	4.614%	$40.3705	$40.37	$40.35	$40.40
Purchase #2	$244.53	11.865%	$273.5435	$273.54	$273.55	$273.50
Purchase #3	$16.83	8.688%	$18.2922	$18.29	$18.30	$18.30
Purchase #4	$53.88	12.192%	$60.449	$60.45	$60.45	$60.40
Purchase #5	$93.38	6.791%	$99.7214	$99.72	$99.70	$99.70
Purchase #6	$41.73	12.815%	$47.0777	$47.08	$47.10	$47.10
Purchase #7	$227.58	8.364%	$246.6148	$246.61	$246.60	$246.60
7 purchase totals =	$716.52		$786.0691	$786.06	$786.05	$786.00