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	$237.37	12.456%	$266.9368	$266.94	$266.95	$266.90
Purchase #2	$79.44	7.648%	$85.5156	$85.52	$85.50	$85.50
Purchase #3	$66.81	8.480%	$72.4755	$72.48	$72.50	$72.50
Purchase #4	$75.71	13.229%	$85.7257	$85.73	$85.75	$85.70
Purchase #5	$208.50	13.833%	$237.3418	$237.34	$237.35	$237.30
Purchase #6	$137.83	3.306%	$142.3867	$142.39	$142.40	$142.40
Purchase #7	$248.27	4.110%	$258.4739	$258.47	$258.45	$258.50
7 purchase totals =	$1,053.93		$1,148.8560	$1,148.87	$1,148.90	$1,148.80