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	$208.53	10.791%	$231.0325	$231.03	$231.05	$231.00
Purchase #2	$55.47	7.587%	$59.6785	$59.68	$59.70	$59.70
Purchase #3	$29.45	12.624%	$33.1678	$33.17	$33.15	$33.20
Purchase #4	$245.66	9.244%	$268.3688	$268.37	$268.35	$268.40
Purchase #5	$54.50	3.448%	$56.3792	$56.38	$56.40	$56.40
Purchase #6	$217.49	4.520%	$227.3205	$227.32	$227.30	$227.30
Purchase #7	$90.39	13.723%	$102.7942	$102.79	$102.80	$102.80
7 purchase totals =	$901.49		$978.7415	$978.74	$978.75	$978.80