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	$14.58	8.607%	$15.8349	$15.83	$15.85	$15.80
Purchase #2	$218.75	5.830%	$231.5031	$231.50	$231.50	$231.50
Purchase #3	$144.38	3.862%	$149.956	$149.96	$149.95	$150.00
Purchase #4	$170.35	9.106%	$185.8621	$185.86	$185.85	$185.90
Purchase #5	$136.97	8.283%	$148.3152	$148.32	$148.30	$148.30
Purchase #6	$99.64	13.233%	$112.8254	$112.83	$112.85	$112.80
Purchase #7	$190.68	12.834%	$215.1519	$215.15	$215.15	$215.20
7 purchase totals =	$975.35		$1,059.4486	$1,059.45	$1,059.45	$1,059.50