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	$75.95	3.863%	$78.8839	$78.88	$78.90	$78.90
Purchase #2	$166.38	12.774%	$187.6334	$187.63	$187.65	$187.60
Purchase #3	$247.75	10.801%	$274.5095	$274.51	$274.50	$274.50
Purchase #4	$65.64	10.511%	$72.5394	$72.54	$72.55	$72.50
Purchase #5	$81.31	9.870%	$89.3353	$89.34	$89.35	$89.30
Purchase #6	$201.90	5.698%	$213.4043	$213.40	$213.40	$213.40
Purchase #7	$95.58	10.302%	$105.4267	$105.43	$105.45	$105.40
7 purchase totals =	$934.51		$1,021.7325	$1,021.73	$1,021.80	$1,021.60