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	$98.81	5.200%	$103.9481	$103.95	$103.95	$103.90
Purchase #2	$74.65	12.106%	$83.6871	$83.69	$83.70	$83.70
Purchase #3	$26.51	4.159%	$27.6126	$27.61	$27.60	$27.60
Purchase #4	$99.94	11.849%	$111.7819	$111.78	$111.80	$111.80
Purchase #5	$229.64	11.211%	$255.3849	$255.38	$255.40	$255.40
Purchase #6	$179.86	11.368%	$200.3065	$200.31	$200.30	$200.30
Purchase #7	$94.90	10.257%	$104.6339	$104.63	$104.65	$104.60
7 purchase totals =	$804.31		$887.3550	$887.35	$887.40	$887.30