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	$42.52	12.548%	$47.8554	$47.86	$47.85	$47.90
Purchase #2	$218.75	8.703%	$237.7878	$237.79	$237.80	$237.80
Purchase #3	$174.47	6.371%	$185.5855	$185.59	$185.60	$185.60
Purchase #4	$14.49	4.727%	$15.1749	$15.17	$15.15	$15.20
Purchase #5	$86.35	9.421%	$94.485	$94.49	$94.50	$94.50
Purchase #6	$15.72	13.738%	$17.8796	$17.88	$17.90	$17.90
Purchase #7	$95.59	10.570%	$105.6939	$105.69	$105.70	$105.70
7 purchase totals =	$647.89		$704.4621	$704.47	$704.50	$704.60