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	$62.91	13.587%	$71.4576	$71.46	$71.45	$71.50
Purchase #2	$74.74	6.345%	$79.4823	$79.48	$79.50	$79.50
Purchase #3	$114.63	4.261%	$119.5144	$119.51	$119.50	$119.50
Purchase #4	$105.61	10.126%	$116.3041	$116.30	$116.30	$116.30
Purchase #5	$13.64	13.179%	$15.4376	$15.44	$15.45	$15.40
Purchase #6	$56.48	5.117%	$59.3701	$59.37	$59.35	$59.40
Purchase #7	$151.63	10.158%	$167.0326	$167.03	$167.05	$167.00
7 purchase totals =	$579.64		$628.5987	$628.59	$628.60	$628.60