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	$87.29	3.577%	$90.4124	$90.41	$90.40	$90.40
Purchase #2	$121.38	9.192%	$132.5372	$132.54	$132.55	$132.50
Purchase #3	$17.87	10.553%	$19.7558	$19.76	$19.75	$19.80
Purchase #4	$225.41	13.481%	$255.7975	$255.80	$255.80	$255.80
Purchase #5	$250.31	9.600%	$274.3398	$274.34	$274.35	$274.30
Purchase #6	$74.47	5.339%	$78.446	$78.45	$78.45	$78.40
Purchase #7	$20.42	12.458%	$22.9639	$22.96	$22.95	$23.00
7 purchase totals =	$797.15		$874.2526	$874.26	$874.25	$874.20