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	$100.51	13.562%	$114.1412	$114.14	$114.15	$114.10
Purchase #2	$217.33	6.156%	$230.7088	$230.71	$230.70	$230.70
Purchase #3	$51.92	5.799%	$54.9308	$54.93	$54.95	$54.90
Purchase #4	$103.86	7.337%	$111.4802	$111.48	$111.50	$111.50
Purchase #5	$206.47	4.782%	$216.3434	$216.34	$216.35	$216.30
Purchase #6	$228.73	4.351%	$238.682	$238.68	$238.70	$238.70
Purchase #7	$21.61	13.582%	$24.5451	$24.55	$24.55	$24.50
7 purchase totals =	$930.43		$990.8315	$990.83	$990.90	$990.70