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	$205.40	9.785%	$225.4984	$225.50	$225.50	$225.50
Purchase #2	$185.29	5.666%	$195.7885	$195.79	$195.80	$195.80
Purchase #3	$206.47	4.383%	$215.5196	$215.52	$215.50	$215.50
Purchase #4	$196.43	9.629%	$215.3442	$215.34	$215.35	$215.30
Purchase #5	$227.70	12.344%	$255.8073	$255.81	$255.80	$255.80
Purchase #6	$63.59	4.667%	$66.5577	$66.56	$66.55	$66.60
Purchase #7	$179.69	5.701%	$189.9341	$189.93	$189.95	$189.90
7 purchase totals =	$1,264.57		$1,364.4498	$1,364.45	$1,364.45	$1,364.40