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	$104.92	7.436%	$112.7219	$112.72	$112.70	$112.70
Purchase #2	$195.66	11.369%	$217.9046	$217.90	$217.90	$217.90
Purchase #3	$192.39	12.697%	$216.8178	$216.82	$216.80	$216.80
Purchase #4	$66.86	8.411%	$72.4836	$72.48	$72.50	$72.50
Purchase #5	$79.29	12.840%	$89.4708	$89.47	$89.45	$89.50
Purchase #6	$212.28	4.304%	$221.4165	$221.42	$221.40	$221.40
Purchase #7	$217.97	13.404%	$247.1867	$247.19	$247.20	$247.20
7 purchase totals =	$1,069.37		$1,178.0019	$1,178.00	$1,177.95	$1,178.00